Substituted birefringent polyamide

ABSTRACT

A class of polyamides comprising recurring units having certain substituted-biphenylene or substituted-stilbene radicals is disclosed. The substituted radicals include substituents so as to confer a non-coplanar molecular configuration and a substantially cylindrical distribution of electron density about the long axis of the recurring units and the chain-extended polymers including such radicals. Molecularly oriented polymers of the invention exhibit optically uniaxial properties. The highly birefringent polymers are suited to application in optical filter and other devices where a refractive and birefringent material is desired.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of our copending U.S. patentapplication, Ser. No. 238,069, filed Mar. 2, 1981, now U.S. Pat. No.4,384,107.

BACKGROUND OF THE INVENTION

This invention relates to a novel class of polymers exhibiting opticallyanisotropic properties. More particularly, it relates to a class ofsubstituted polyamides having a highly birefringent character.

Materials having a birefringent character have been variously applied inconnection with the construction of filter and other optical devices.Frequently, a birefringent element utilized in an optical filter orother device will comprise a plate made from a monocrystalline form ofbirefringent optical material. Single crystals are expensive materialsand are not readily formed to the desired shape or conformation requiredin particular applications. The size to which such crystals can be grownrepresents an additional limitation on the utilization of such materialsin optical devices.

Optical devices including a birefringent material in the form of apolymeric layer, such as may be formed by the unidirectional stretchingof a suitable polymeric material, have also been described. Thus,light-polarizing devices utilizing a polymeric birefringent layer havebeen described in U.S. Pat. No. 3,213,753 (issued Oct. 26, 1965 to H. G.Rogers). Optical devices including polymeric birefringent materials havealso been set forth, for example, in U.S. Pat. No. 3,506,333 (issuedApr. 14, 1970 to E. H. Land) and in U.S. Pat. No. 3,610,729 (issued Oct.15, 1971 to H. G. Rogers). Frequently, the efficiency of an opticalfilter, polarizing or other optical device including a birefringentelement or layer will depend upon the realization of large netdifferences in refractive index between birefringent material andadjacent or contiguous materials. In general, such net differences willbe maximized where a birefringent material is highly birefringent.Correspondingly, large net differences in refractive indices ofcontiguous materials will be unattainable where birefringent polymericmaterials otherwise suited to application in an optical device tend toexhibit either low or only marginal birefringent character. Accordingly,polymeric materials exhibiting a highly birefringent character will beof particular interest for optical applications and enhanced efficiency.

SUMMARY OF THE INVENTION

The present invention provides a class of polymers exhibiting highbirefringence and is based in part upon the discovery that theincorporation into a polyamide of certain divalent substituted aromaticradicals, in the form of substituted aromatic radicals having thephenylene moieties thereof in a non-coplanar molecular configuration,imparts to the polyamide material an unusually high anisotropic orbirefringent character. Transparent polymeric materials exhibitinguniaxial optical properties, i.e., only two indices of refraction, areprovided by the present invention. These polymers comprise certainrepeating or recurring units in chain-extended relation, the recurringunits including divalent substituted aromatic radicals. The presence ofsubstituent groups in the recurring units such that the aromatic nucleithereof are in a non-coplanar molecular configuration permits theprovision of a substantially cylindrical distribution of electrondensity about the long axis of the polymer and the realization of highbirefringence. There is thus simulated in a polymeric material opticalproperties of a uniaxial crystal. The present invention, thus, providesa class of polymers comprising recurring units of the formula ##STR1##wherein each of A and B is a divalent radical, except that B canadditionally represent a single bond; R and R¹ are each hydrogen, alkyl(e.g. methyl, ethyl), aryl (e.g., phenyl, naphthyl), alkaryl (e.g.,tolyl), or aralkyl, (e.g., benzyl); and c is zero or one; and wherein,when c is one, at least one of A and B is a divalent radical selectedfrom the group consisting of: ##STR2## where each U is a substituentother than hydrogen, each W is hydrogen or a substituent other thanhydrogen, and each p is an integer from 1 to 3, said U and Wpsubstitution being sufficient to provide said radical with a noncoplanarmolecular configuration; and ##STR3## where each of Y and Z is hydrogenor a substituent other than hydrogen and each t is an integer from 1 to4, with the proviso that when each said Z is hydrogen, at least one saidY substituent is a substituent other than hydrogen positioned on thecorresponding nucleus ortho with respect to the ##STR4## moiety of saidradical, said Z and Y_(t) substitution being sufficient to provide saidradical with a non-coplanar molecular configuration;

and wherein, when c is zero, A is a divalent radical selected from thegroup consisting of radicals (1) and (2) as hereinbefore defined.

THE DRAWINGS

FIG. 1 is a geometric representation of molecular dimensions of a repeatunit of a polymeric material of the invention.

FIG. 2 is a cross-sectional view along the line 1--1 of FIG. 2.

FIG. 3 is a vectorial representation of bond and group polarizabilitiesof a repeat unit of a polymeric material of the invention.

FIGS. 4a and 4b show, respectively, ellipsoidal and circularcross-sectional distribution of electron density about the long axis ofa recurring unit of a polymeric material of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As described hereinbefore, the substituted polyamides of the presentinvention comprise recurring units of the formula ##STR5## wherein c iszero or one and wherein A (when c is zero) or at least one of A and B(when c is one) comprises a substituted divalent biphenylene radical ora substituted divalent stilbene radical. Thus, when c is zero, divalentradical A comprises a substituted biphenylene radical having anon-coplanar molecular configuration or a substituted divalent stilbeneradical of non-coplanar molecular configuration. Similarly, when c isthe integer one, one or both of divalent radicals A and B comprises suchsubstituted-biphenylene or substituted-stilbene radicals.

The molecularly oriented and highly birefringent polymers of the presentinvention comprise repeating molecular units represented by thestructure of Formula I. These units exhibit high electron densitysubstantially cylindrically distributed about the long axis thereof. Theoptically uniaxial character of molecularly orientedsubstituted-biphenylene and substituted-stilbene polyamides of thepresent invention is importantly related to the molecular configurationor structure of the substituted-biphenylene and/or substituted-stilbeneradicals of the repeating units of the polymer and to the distributionof electron density. The presence of substituent groups on thebiphenylene and/or stilbene radicals such that the phenylene moietiesthereof are in a non-coplanar relation to one another so as to provide asubstantially cylindrical distribution of electron density about thelong axis of the polymer and the recurring units thereof permits therealization of high birefringence and the simulation in a polymericmaterial of optical properties of a uniaxial crystal.

The birefringence of oriented polymers of the present invention can berepresented in relation to molecular configuration and electron densitydistribution according to a dimensionless geometric index G set forth bythe relationship: ##EQU1## wherein E is a dimensionless eccentricityfactor defined by the relationship ##EQU2## where e_(L) is thelongitudinal eccentricity of the polarizability of the repeatingmolecular unit and e_(T) is the transverse eccentricity of the electronpolarizability of the repeating molecular unit, L is the length of therepeating molecular unit along the main axis thereof and D is the meandiameter of the repeating molecular unit. The contribution tobirefringence of the molecular structure of a repeating, chain-extendingunit of a substituted-biphenylene or substituted-stilbene polyamide ofthe present invention will be better understood by reference to thedrawings hereof.

In FIG. 1 is shown a geometrical representation of a repeatingchain-extending molecular unit of a polymeric material of the presentinvention. Each repeating unit may thus be visualized as a repeatingrod-like segment of finite length L and of a generally cylindricalconfiguration. Birefringence has been found to be importantly related tothe molecular structure of the repeating units of the polymer inaccordance with the relationship of geometric index G, set forthhereinbefore. A highly birefringent polymeric material of the inventionwill comprise a plurality of molecular units in chain-extendedrelationship, each unit having a length L, shown in FIG. 1. The longaxis X of each repeating unit forms, in the chain-extended polymer, thelong axis or backbone. Each axis in FIG. 1 forms a right angle withrespect to any other axis. The mean diameter D, set forth in thegeometric index G, is determined for each repeating unit by theexpression D=(Y+Z)/2. In FIG. 2 is shown along line 1--1 of FIG. 1, across-sectional view. The shown Y and Z axes are at right angles to oneanother, the X axis comprising the axis of the cylinder extending in adirection normal to the plane of the paper.

In addition to a rigid rod-like geometry in a polymeric material as theresult of an end-to-end combination of repeating units hereof, theelectron density distributed around the long axis of the polymer,variously treated as a cylindrical or ellipsoidal distribution, isbelieved to comprise a major contributing factor to optical anisotropyor birefringence. High electron density substantially cylindricallydistributed around the long axis of a polymer is exhibited in a polymerof coaxially-bonded repeating units comprising non-coplanar,particularly orthogonal, substituted biphenylene and/orsubstituted-stilbene radicals. An orthogonal relationship betweenadjacent phenylene rings can be nearly attained by the placement ofsubstituents with large steric effects on the ortho-positions of nextadjacent phenylene rings. In FIG. 3 is shown a vectorial representationof bond and group polarizabilities of a repeating unit of a polymer ofthe invention. It will be appreciated that electron density distributionabout axis X will be variously treated as a cylindrical or ellipsoidaldistribution depending upon the relative magnitudes of the Y and Zvectors. In FIG. 4a is shown an ellipsoidal cross-section along the axisof FIG. 3 where the magnitude of the shown Y vector is greater than thatof the Z vector. Ideally, Y and Z vectors would be equal and theresulting circular cross-sectional distribution along the X axis isshown in FIG. 4b.

By a combination of longitudinal eccentricity (e_(L)) and transverseeccentricity (e_(T)), based upon bond and group polarizabilities, andthe length and mean diameter of a repeating unit, a geometric index, G,related to optical anisotropy or birefringence, can be represented asfollows: ##EQU3## wherein e_(L), e_(T), L and D have the meaningshereinbefore ascribed. Longitudinal eccentricity e_(L) may berepresented according to the following relationship ##EQU4##

Transverse eccentricity e_(T) may be represented by the relationship##EQU5## wherein the magnitude of vector Y is the larger of the Y and Zvectors. Ideally, transverse eccentricity e_(T) will equal zero andlongitudinal eccentricity e_(L) will equal one, in which case, theeccentricity factor, E, will equal the theoretical maximum of two.

Geometric index G can be calculated for repeating units of a rigidrod-like polymeric material of the present invention by resort to meandiameter and length values and longitudinal and transverse eccentricityvalues calculated from experimentally determined dihedral angles. Itwill be appreciated that the magnitude of values of length, meandiameter, longitudinal eccentricity and transverse eccentricity willmaterially influence the value of geometric index G. Thus, it will beappreciated that a repeating unit having, for example, a length of abouttwice that of a repeating unit having a different molecular structureand configuration will have a geometric index of about twice that ofsuch different repeating unit. Accordingly, in making comparisons ofgeometric indices and magnitude thereof in relation to structuraldifferences between comparative molecular repeating units, suchdifferences in length should be borne in mind.

In general, experimentally determined values of birefringence forpolymers comprised of repeating units as aforedescribed, will correlatedirectionally with values of geometric index, G, of the repeating units.Thus, recurring units having higher geometric index values, will, ingeneral, provide polymers exhibiting higher birefringence. Polymericmaterials comprised of repeating units as aforedescribed, depending uponthe nature of substituent groups and the influence thereof on electrondensity distribution, will generally be comprised of repeating unitshaving a geometric index value, G, of about 0.8 or higher. It will bepreferred, however, that polymeric materials hereof comprise repeatingunits having geometric index values of one or higher. Especiallypreferred herein are polymers comprising repeating units of geometricindex value of 1.2 or higher.

High birefringence observed in the case of substituted-biphenylene andsubstituted-stilbene polyamides comprised of recurring units of highgeometric index value (G) is believed to be importantly related to thepresence in such units of phenylene rings in "twisted" relation to oneanother, i.e., where the phenylene rings are in non-coplanar molecularconfiguration with respect to each other or, preferably, in mutuallyorthogonal planes. It has been found, for example, in the case ofsubstituted-biphenylene polyamides, that the presence of substituentmoieties on the ortho-positions of interbonded phenylene rings, of atype such as to effect a non-coplanar molecular configuration withrespect to the interbonded phenylene rings, provides a recurring unithaving a high geometric index. The condition of non-coplanarity amongphenylene rings in such a recurring unit, or presence in such units ofrings in "twisted" configuration relative to one another has been foundto be importantly related to high birefringence in the rigid rod-likeoriented polymers resulting from the end-to-end joining of suchrecurring units. Similarly, the presence of substituents on the vinyleneor aromatic nuclei of a stilbene radical promotes a condition ofnon-coplanarity among such nuclei and high geometric index andbirefringence.

As described hereinabove, birefringent substituted-biphenylene andsubstituted-stilbene polyamides of the present invention include thosecomprising recurring units of the formula ##STR6## wherein C is zero orone. It will be appreciated that polyamides comprising the followingrecurring units are contemplated when c is one: ##STR7## In suchrecurring units, at least one of divalent radicals A and B will comprisea substituted-biphenylene or substituted-stilbene radical ofnon-coplanar molecular configuration conforming to the formulae:##STR8##

In the case of substituted-biphenylene radicals A and/or B of the typerepresented by Formula III, U will comprise a substituent other thanhydrogen; W will comprise hydrogen or a substituent other than hydrogen;and p will be an integer of from 1 to 3. It will be appreciated from thenature of U, W and p, as set forth, that each aromatic nucleus of thebiphenylene radical represented by Formula III will be substituted atthe ortho-position by a moiety other than hydrogen and that eachinterbonded phenylene ring can contain additional substituents.Preferably, each W of each phenylene ring will be hydrogen such that thesubstituted-biphenylene radical of Formula III has the followingstructure: ##STR9## wherein each U substituent, as defined, is asubstituent other than hydrogen. It will be appreciated that polymericmaterials comprised of such recurring units will be preferred from thestandpoint of ease of preparation.

The nature of substituents U and W of the biphenylene radical of FormulaIII can vary widely, consistent with the provision of a biphenyleneradical having a non-coplanar molecular configuration. As used herein,the term non-coplanar molecular configuration refers to a molecularconfiguration whereby the two aromatic nuclei of the biphenylene radicalare in different planes.

While applicants do not wish to be bound by precise theory or mechanismin explanation of the highly birefringent character observed in orientedpolymers comprising recurring units of high geometric index, it isbelieved that such character is importantly related to thenon-coplanarity conferred or promoted by the presence of substituents inthe aforedescribed recurring units. It is believed that theortho-positioning of atoms or moieties other than hydrogen on theinterbonded nuclei of a biphenylene radical materially reducescoplanarity. This non-coplanarity provides a distribution of highelectron density substantially cylindrically about the long axis of thepolymer. This distribution of electron density is believed to contributeat least in part to unusually high birefringence observed in suchpolymers.

The nature of substituency U and Wp should be such as to provide thebiphenylene radical of Formula III with a non-coplanar molecularconfiguration referred to hereinbefore. Such configuration will in partbe determined by the size of non-hydrogen U substituents on the aromaticnuclei of the biphenylene radical and upon the number and positioning ofany other non-hydrogen substituents as may be substituted on sucharomatic nuclei. For example, where the interbonded aromatic nucleicontain large or bulky U substituents, such as trifluoromethyl groups,the desired condition of non-coplanarity is more readily realized.Similarly, where the U substituents are relatively small, such as chlorogroups, an additional non-hydrogen W substituent at the ortho-positionof each nucleus can increase desired non-coplanarity. Suitable Usubstituents herein include halogen (e.g., fluoro, chloro, bromo, iodo);nitro; alkyl (e.g., methyl, ethyl); alkoxy (e.g., methoxy);trifluoromethyl; cyano; hydroxy; hydroxyalkyl (e.g., hydroxyethyl);thioalkyl (e.g., thiomethyl); carboxy; sulfonic acid esters; sulfinicacid esters, carboxamide; sulfonamide; amino; and carbonyl. Eachsubstituent W can comprise hydrogen or a substituent other than hydrogenas set forth in connection with substituent U. Preferably, each W willbe hydrogen and each p will be the integer 3.

Preferred polyamides herein are the polyamides comprising recurringunits having the biphenylene radical of Formula V, i.e., ##STR10##wherein each U, which may be the same or different, is halo, nitro,alkoxy or substituted-alkyl, such as trifluoromethyl.

In the polyamides of the present invention which comprise recurringunits represented by the following formula ##STR11## either or both ofradicals A and B can comprise the substituted stilbene radical set forthhereinbefore as Formula IV, i.e., ##STR12## In such stilbene radicals,the nature of each Y and Z will be such as to provide the radical with anon-coplanar molecular configuration. Preferably, non-coplanarity willbe provided by the presence of a single non-hydrogen substituent Z.Where each Z is hydrogen, non-coplanarity can be provided by thepositioning of a non-hydrogen Y substituent on at least one aromaticnucleus of the radical in an ortho relationship to the ##STR13## moityof the radical. Suitable non-hydrogen Y and Z substituents include, forexample, any of those set forth in connection with radicals U and Wdefined hereinbefore.

Examples of the preferred substituted-stilbene radicals included withinthe class represented by Formula IV include the following: ##STR14##wherein at least one of the Y substituents is other than hydrogen,preferably, halo or alkoxy; and ##STR15## where Z is a substituent otherthan hydrogen, preferably halo.

Where only one of said A and B radicals is a substituted-biphenylene orsubstituted-stilbene radical conforming to the radicals represented bythe structures of Formulas III and IV, the remaining A or B radical cancomprise any of a variety of divalent radicals so long as thebirefringent properties of the polyamide material are not effectivelynegated. In general, where only one of the A and B radicals conforms tothe structures represented by the Formulas III and IV, the remaining Aor B radical will desirably be a divalent radical which does not confertransverse eccentricity to the recurring unit. Similarly, where one ofradicals A or B is a radical which confers transverse eccentricity tothe recurring unit, the other of radical A or B will desirably be aradical which confers high longitudinal eccentricity such that therecurring unit of the polymer exhibits a high geometric index.

When only one of radicals A and B is a substituted-biphenylene orsubstituted-stilbene radical, the other of A or B can be any of avariety of divalent radicals including, for example, unsubstitutedbiphenylene or stilbene radicals; phenylene; transvinylene; orethynylene. Also suitable are polyunsaturated divalent radicalsconforming to the formula ##STR16## where n is an integer of at leasttwo (e.g., two or three) and each of D and E is hydrogen or alkyl (e.g.,methyl) and inclusive of such polyunsaturated divalent radicals astrans-trans-1,4-butadienylene, i.e., ##STR17## and1,4-dimethyl-trans-trans-1,4-butadienylene, i.e., ##STR18## It will beappreciated that compounds containing amino groups directly attached tocarbon atoms having aliphatic unsaturation are not stable. Accordingly,the aforesaid vinylene, ethynylene and butadienylene radicals cannotserve as B radicals in the recurring units represented by the structureof Formula II.

Where only one of radicals A and B is substituted-biphenylene radical ofFormula III or a substituted-stilbene radical of Formula IV, the otherof A or B can be a radical which does not conform to the structure ofFormula II but which has a non-coplanar molecular configuration and asubstantially cylindrical distribution of electron density about thelong axis thereof.

In general, from the standpoint of maximized birefringent properties, itwill be preferred that each of radicals A and B comprise a divalentsubstituted-biphenylene or substituted-stilbene radical exhibiting anon-coplanar molecular configuration and conforming to the structures ofFormulas III or IV. It will be appreciated, however, that the particularnature of such A and B radicals may affect the capacity of the polyamidematerial to be readily oriented, as by extrusion, stretching or thelike. Accordingly, where the capacity of a polyamide material to beoriented is effectively reduced by the presence in the polyamide of eachof radicals A and B of non-coplanar molecular configuration andconforming to the structure of Formula III or IV, it will be preferredthat only one of such radicals A and B of the polyamide material conformto the structure thereof.

Inclusive of polyamides of the present invention represented by thestructure of Formula II are those having recurring units represented bythe following structures wherein, unless otherwise specified, U, W, p,Y, Z and t have the meanings set forth hereinbefore: ##STR19##

From inspection of the general formula set forth as descriptive ofrecurring units of the polyamides of the present invention, i.e.,recurring units of the formula ##STR20## it will be appreciated that,when c is zero, the recurring units will be represented by the followingformula: ##STR21## In such recurring units, radical A will comprise adivalent radical having a non-coplanar molecular configuration andconforming to the structures of Formulas III and IV set forthhereinbefore, i.e., ##STR22## where U, W, p, Y, t and Z have the samemeanings.

Inclusive of polyamides of the present invention represented by thestructure of Formula XVIII are those having recurring units representedby the following structures wherein U, W, p, Y, Z and t, unlessotherwise indicated, have the meanings set forth hereinbefore: ##STR23##where Z is other than hydrogen.

While the substituted-biphenylene and substituted-stilbene polyamidesdescribed heretofore consist essentially of recurring units representedby the structures of Formulas III and XVI, i.e., recurring units of theformulas ##STR24## a combination of such recurring units, thesubstituted polyamides can also comprise recurring units not conformingto the described structures of Formulas III and XIV. Examples ofrecurring units which do not conform to such descriptions and which canbe present in such polyamides in proportions which do not negate thehigh birefringence of the polymeric materials include, for example,recurring units having the formulas ##STR25## wherein G is a divalentradical such as 1,4-phenylene; 4,4'-biphenylene; vinylene;trans,trans-1,4-dimethyl-trans,trans-1,4-butadienylene;2,4'-trans-vinylenephenylene; trans,trans-4,4'-bicyclohexylene;2,5,7-bicyclooctatriene-1,4-, i.e., ##STR26##

Divalent radical G can also comprise radicals having a non-coplanarmolecular configuration and a substantially cylindrical distribution ofelectron density about the long axis thereof. Other divalent radicalscan, however, serve as radical G provided that such radicals do notadversely and materially reduce the birefringence of the polyamidematerial. It will be appreciated that G cannot represent an aliphaticunsaturated moiety where such moiety is to be bonded between two aminogroups.

The polyamides of the present invention can be prepared by resort topolyamide synthesis routes involving the polymerization of suitable acidhalide and amine monomers in an organic solvent which may contain asolubilizing agent such as lithium chloride or chain-terminating agentwhere desired. Polyamides of the type represented by the structure ofFormula I can be prepared, for example, by reaction of a dicarboxylicacid halide of the formula ##STR27## with a diamine of the formula##STR28## where Hal represents halogen, such as chloro or bromo and Aand B have the meanings hereinbefore set forth, except that B cannotrepresent an aliphatic unsaturated moiety. Where B desirably representsa single bond in the polymers hereof, the aforesaid dicarboxylic acidhalide of the formula ##STR29## can be suitably reacted with hydrazine.The polymers of the present invention can be prepared in an organicsolvent such as N-methyl pyrrolidone (NMP), tetramethylurea (TMU) or amixture thereof, and preferably, in the presence of a salt such aslithium chloride to assist in the solubilization of reactant monomersand maintenance of a fluid reaction mixture. The preparation of apolyamide of the present invention can be illustrated by reference tothe preparation of poly(2,2'-dibromo-4,4'-biphenylene)-trans--bromo-p,p'stilbene dicarboxamide, a preferred polyamide herein, inaccordance with the following reaction scheme: ##STR30##

Polyamides containing recurring units having the structure representedby Formula XVII, i.e., ##STR31## can be prepared, for example, by thepolymerization of a p-amino-aroyl halide monomer in the form of ahalide, arylsulfonate, alkylsulfonate, acid sulfonate, sulfate or othersalt. This polymerization can be illustrated by reference to thepreparation of poly(2,2'-dibromo-4,4'-biphenylene)carboxamide inaccordance with the following reaction scheme showing the polymerizationof the hydrochloride salt of2,2'-dibromo-4-amino-4'-chlorocarbonylbiphenyl: ##STR32##

The substituted polyamides of the present invention can be prepared bypolymerization of correspondingly substituted monomers in a suitableorganic reaction solvent. Such solvents include amide and urea solventsincluding N-methylpyrrolidone and N,N,N'N'-tetramethylurea. Othersuitable reaction solvent materials include N-methylpiperidone-2;N,N-dimethylpropionamide; N-methylcaprolactam; N,N-dimethylacetamide;hexamethylphosphoramide; and N,N'-dimethylethyleneurea. Thepolymerization can be conducted by dissolving the monomer or monomers tobe polymerized in the reaction solvent and allowing the exothermicpolymerization reaction to occur usually with the aid of externalcooling. In general, the polymerization will be conducted initially at atemperature of from about -20° C. to about 15° C., and preferably, inthe range of from about -5° C. to about 5° C. Thereafter, usually withinabout one-half hour to one hour, the reaction will be heated withformation of a thickened polymeric mass of gel-like consistency. Ingeneral, the polymerization reaction will be conducted over a period offrom about 1 to 24 hours, preferably about 3 to 18 hours.

While the monomer or monomers to be polymerized can be dissolved in asuitable amide or urea solvent and allowed to react with formation ofthe desired polymeric material, a preferred reaction sequence where amixture of copolymerizable monomers is utilized involves the preparationof a solution of a first monomer in the amide or urea solvent and theaddition thereto of a second or other monomer or a solution thereof in asuitable organic solvent therefor, such as tetrahydrofuran. Externalcooling of the resulting reaction mixture provides the desired polyamidematerial in high molecular weight and minimizes the production ofundesired side reactions or by-products.

The polyamide materials prepared as described can be recovered bycombining the polymerization reaction mixture with a non-solvent for thepolymer and separating the polymer, as by filtration. This can beeffectively accomplished by blending the polymerization mixture withwater and filtering the solid polyamide material. The polyamide can bewashed with an organic solvent such as acetone or ether and dried, forexample, in a vacuum oven.

Starting materials for the preparation of substituted polyamides of theinvention can be prepared by resort to known synthetic methods. Forexample, the reactant 2,2'-dibromobenzidine (utilized as a reactant inthe production of the polyamides of EXAMPLES 1, 3, 5, 7, 8 and 9 hereof)can be prepared by an electrophilic bromo-substitution of4,4'-dinitrobiphenyl (as by reaction with bromine and silver sulfate inthe presence of sulfuric acid) followed by a reduction of the nitrogroups of the resulting 2,2'-dibromo-4,4'-dinitrobiphenyl compound bythe action, for example, of stannous chloride and hydrochloric acid.This preparative route is set forth in the following reaction scheme:##STR33##

The reactant 2,2'-dibromo-4,4'-biphenylene dicarbonyl chloride (utilizedin the production of the polyamides of EXAMPLES 3 and 4 hereof) can beprepared from dimethyl 4,4'-biphenylene dicarboxylate by anelectrophilic bromo-substitution utilizing bromine and silver sulfate inthe presence of sulfuric acid, followed by acid hydrolysis andconversion of the resulting 2,2'-dibromo-4,4'-biphenylene dicarboxylicacid to the corresponding acid chloride by reaction with thionylchloride. This synthesis is set forth in the following reaction scheme:##STR34##

The reactants 2,2'-dinitro-4,4'-biphenyl dicarbonyl chloride and2,2'-dinitrobenzidine (each utilized in the production of the polyamideof EXAMPLE 2 hereof) can be prepared from the methyl ester of3-nitro-4-bromo-benzoic acid via a coupling reaction. The methyl esterof 3-nitro-4-bromo-benzoic acid is coupled with the aid of copper in thepresence of dimethylformamide with provision of dimethyl2,2'-dinitro-4,4'-biphenylene dicarboxylate. Acid hydrolysis yields thecorresponding diacid compound 2,2'-dinitro-4,4'-biphenylene dicarboxylicacid. The diacid compound can be reacted with thionyl chloride (forconversion to 2,2'-dinitro-4,4'-biphenyl dicarbonyl chloride) or can berearranged by the action of sodium azide and sulfuric acid (forproduction of 2,2'-dinitrobenzidine). These reaction schemes areillustrated as follows: ##STR35##

The starting compound 2,2',3,3',5,5',6,6'-octa-fluoro-4,4'-biphenylenedicarbonyl chloride (utilized in the production of the polyamides ofEXAMPLES 5 and 6 hereof) can be prepared by reaction of4,4'-dibromo-2,2',3,3',5,5',6,6'-octafluorobiphenyl with butyl lithiumin hexane followed by reaction with carbon dioxide and reaction of theresulting octafluoro biphenylene dicarboxylic acid with thionyl chloridein accordance with the following scheme: ##STR36##

The substituted-stilbene starting material α-bromo-p,p'-stilbenedicarbonyl chloride (utilized in the manufacture of the polyamide ofEXAMPLE 8 hereof) can be prepared from p,p'-stilbene dicarboxylic acidby reaction with thionyl chloride, formation of the dimethyl ester byreaction with methanol and bromination of the resulting dimethyl ester.Reaction of the product with potassium hydroxide in alcohol yields thecis-α-bromo-dimethyl ester of stilbene dicarboxylic acid, which uponirradiation, is converted to the trans-isomer. Acid hydrolysis followedby reaction with thionyl chloride provides the desired reactant. Thesynthetic route is illustrated by the following reaction scheme:##STR37##

The substituted polyamides of the present invention can be variouslyformed or shaped into films, sheets, coatings, layers, fibrils, fibersor the like. For example, a solution of polyamide in a solvent materialsuch as N,N-dimethylacetamide, preferably containing lithium chloridesolubilizing agent, can be readily cast onto a suitable support materialfor the formation of a polymeric film or layer of the polyamidematerial. The polymeric film can be utilized for the production of abirefringent polymeric film or sheet material. Thus, the polymeric filmor sheet material can be subjected to stretching so as to introducemolecular orientation and provide a film material having a highlybirefringent character.

The substituted polyamides of the present invention can also be formedinto fibers, fibrils or the like by extrusion or spinning methods knownin the art. Thus, for example, a solution of polyamide of the presentinvention in a solution such as N,N-dimethylacetamide containing lithiumchloride can be extruded or spun into a coagulating bath for coagulationof the polymeric material into the form of fibers which can be cut,stretched or assembled into fiber tows or bundles as desired. Thefibers, fibrils, tows or the like can be washed for removal of residualsolubilizing agents, solvents, extruding or spining aids and dried tomaterials exhibiting birefringent properties.

The substituted polyamides of the present invention are especiallyadvantageous from the standpoint of the provision of material exhibitinghigh birefringence. The substituted polyamides hereof, as prepared andin solution in a suitable reaction solvent, exist in an unoriented andnon-birefringent form. The substituted polyamides respond, however, tostress and exhibit birefringent character. Thus, solutions of thesubstituted polyamides hereof, upon the application of slight stress,exhibit streaming birefringence, which can be observed by placement ofthe stressed material between crossed polarizers' and observation of thetransmission of light therethrough as the result of depolarization oflight by the stressed birefringent polyamide material. The property ofstreaming birefringence observed in this manner with the aid of crossedpolarizers is not visually detected by inspection of the clear,transparent polymer solution and is to be distinguished from thestress-induced satin-like sheen or pearlescence characteristic ofmaterials exhibiting stir opalescence. The streaming birefringenceexhibited by the substituted polyamides hereof (upon the application ofstress) will normally be rapidly extinguished upon relaxation of thestress. Where a molecular orientation is permanently induced in thepolyamide material, as by formation of the polyamide material into anoriented sheet, fiber or other form, the polyamide will exhibit opticalbirefringence which can be measured in accordance with a number of knownmethods.

The substituted polyamides of the present invention can be effectivelyoriented by known shaping or forming methods. Preferably, this will beaccomplished by unidirectional stretching of a polymeric film, byextrusion of the polymer into a sheet, fiber, fibril or other stretchedform, or by the combined effects of extrusion and stretching. In theiroriented state, the polymers of the present invention exhibit unusuallyhigh birefringence. In general, greater birefringence will be observedin the case of polymeric materials exhibiting a greater degree ofmolecular orientation. It will be appreciated, however, as has beenpointed out, hereinbefore, that the particular structure of thepolyamide may affect the physical attributes of the polymer material orotherwise impose a practical limitation upon the degree of orientationthat can be realized by stretching or other means. It is a significantaspect of the present invention, however, that the substitutedpolyamides hereof, particularly for a given degree of orientation,exhibit unusually high birefringence. In this connection, it is to benoted that the substituted polyamides hereof will often exhibit higherbirefringence than more highly oriented materials of different polymericstructure. For example, an extruded film of a substituted polyamidehereof comprised of recurring units of the formula ##STR38## and havinga degree of orientation in the range of from about 80% to 85% asdetermined from infra-red dichroism, exhibited a birefringence (Δn) of0.865 as measured utilizing principles of interferometry. In contrast, apolyamide fiber material and comprised of recurring units of the formula##STR39## is reported in the literature, A. A. Hamza and J. Sikorski, J.Microscopy, 113, 15 (1978), as having a birefringence of 0.761, asmeasured by interferometric technique and at a degree of orientation ofabout 90% to 95%.

The substituted polyamides of the present invention, in addition toexhibiting high birefringent properties, are advantageous from thestandpoint of their utilization for the production of transparentpolymeric forms. In contrast to polymeric materials which becomedecidedly opaque as a result of stretching, the polyamides hereofexhibit transparency in unoriented and stretched forms. The substitutedpolyamides of the invention exhibit a high transparency and a low orderof light scattering, exhibiting a ratio of amorphous to crystallinematerial of from about 10:1 to about 20:1 by weight. The polyamides ofthe invention are, thus, suited to optical applications where alight-transmissive, highly refractive and birefringent material isdesirably utilized. Depending upon the nature of substituent moieties onthe divalent radicals of the recurring units of the polyamides of theinvention, colorless or nearly colorless polymeric films or fibers canalso be fabricated. Where, for example, nitro-substituted biphenyleneradicals are present, a yellow transparent film or fiber can befabricated. Films, coating, fibers or other shaped forms of thesubstituted polyamides can be redissolved and reshaped or refabricatedif desired. Depending upon the nature of particular recurring units ofthe polyamide materials, and particularly the nature of substituentmoieties and solvent materials, the solubility characteristics of thesubstituted polyamides of the invention can be varied or controlled tosuit particular applications.

The birefringent property of the polymers of the present invention canbe determined by the measurement of physical and optical parameters inaccordance with known principles of physics and optics. Thus, forexample, the birefringence (Δn) of a substituted polyamide material ofthe invention can be determined by the measurement of optical phaseretardation (R) and film thickness (d) and calculation of birefringencein accordance with the relationship

    Δn=(Rλ/d)

where λ represents the wavelength of light utilized for the conduct ofthe measurements. Alternatively, parallel refractive index andperpendicular refractive index of the film material can be measuredutilizing Becke line analysis or critical angle measurement.

A preferred method for determining the birefringence of the substitutedpolyamides of the invention involves the measurement of retardation ofthe polyamide material by a method utilizing principles ofpolarized-light microscopy and interferometry. Such method providesdesired precision and accuracy in the measurement of the phasedifference between a sample ray passing through a sample of polyamidematerial and a reference ray passing through a neighboring empty area(embedding medium or air) of the same thickness. The light emitted by alow-voltage lamp of a microscope is linearly polarized by passagethrough a polarizer and, in turn, is passed through a condenser, acalcite plate beam splitter, a half-wave retarder plate, the polymericsample, a beam recombinator calcite plate, and through an analyzer whosetransmission direction is vertical to that of the polarizer (crossedposition). In the analyzer the components vibrating in its absorptiondirection are extinguished, whereas the components of both rays in thetransmission direction are transmitted and interfere. The phasedifference between sample and reference beams, caused by the molecularbetween sample and reference beams, caused by the molecular structure ofconfiguration of the polymeric sample, is measured with compensators.From these measurements, the thickness and refractive index of thepolymeric material can be determined. By determining index of refractionof the polymeric sample for both parallel and perpendicular directions,birefringence can, by difference, be determined. A suitable method andapparatus for determining phase retardation, index of refraction andbirefringence for the substituted polyamides of the present invention isa pol-interference device according to Jamin-Lebedeff described ingreater detail by W. J. Patzelt, "Polarized-light Microscopy", ErnestLeitz GmbH, Wetzlar, West Germany, 1974, page 92.

The substituted polyamides of the present invention can be utilized inthe construction of a variety of optical filter or other devices.Suitable devices include multilayer devices which include, for example,a layer of molecularly oriented and birefringent polymeric material and,in addition, at least one other layer of isotropic or birefringentmaterial. The additional layer or layers or such devices, whetherisotropic or birefringent, will generally comprise materials having anindex of refraction matching substantially one index of refraction ofthe highly birefringent polymeric material of the invention. Forexample, a layer of isotropic material having an index of refractionmatching substantially one index of refraction of the highlybirefringent layer can be suitably bonded to the layer of highlybirefringent polymer. A preferred device comprises a layer of themolecularly oriented and highly birefringent material of the inventionbonded between two layers of isotropic material, the index of refractionof each isotropic layer constituting substantially a match with an indexof refraction of the molecularly oriented and highly birefringentmaterial. Such a preferred device can be utilized for the polarizationof light and may be termed a "total transmission" light polarizer, i.e.,one which is particularly adapted to polarize a very large portion ofincident light. Total polarizers find application in equipment such asmay be employed for signaling, projection and display purposes, or thelike, and in antiglare systems for automotive vehicles.

According to another application of the polymeric materials of thepresent invention, a plurality of alternating isotropic and birefringentlayers can be utilized for the production of a multilayer lightpolarizing device, at least one of the layers of birefringent materialcomprising a molecularly oriented and highly birefringent material asdefined herein. Such a device can be utilized as a multilayer polarizerwhich partly transmits and partly reflects incident light as separatelinearly polarized components vibrating in orthogonal directions.

Optical devices in which the substituted polyamides of the invention canbe utilized, and their methods for construction and modes of operationare described in detail in the copending U.S. patent application of H.G. Rogers, et al., Ser. No. 238,054, filed Mar. 2, 1981. Examples ofother devices which can be adapted to include a polymeric and highlybirefringent layer as described herein are described, for example, inU.S. Pat. No. 3,506,333 (issued Apr. 14, 1970 to E. H. Land;) in U.S.Pat. No. 3,213,753 (issued Oct. 26, 1965 to H. G. Rogers); in U.S. Pat.No. 3,610,729 (issued Oct. 5, 1971 to H. G. Rogers); in U.S. Pat. No.3,473,013 (issued Oct. 14, 1969 to H. G. Rogers); in U.S. Pat. No.3,522,984 (issued Aug. 4, 1970 to H. G. Rogers); in U.S. Pat. No.3,522,985 (issued Aug. 4, 1970 to H. G. Rogers); in U.S. Pat. No.3,528,723 (issued Sept. 15, 1970 to H. G. Rogers); and in U.S. Pat. No.3,582,424 (issued June 1, 1971 to K. Norvaisa).

The following non-limiting examples are illustrative of the presentinvention.

EXAMPLE 1

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-p,p'-biphenylene dicarboxamide and thepreparation therefrom of birefringent polymeric films.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.63 grams ofanhydrous lithium chloride and 0.5746 gram (0.001679 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple (a rubber membrane-like sealing lid capable of receiving asyringe and of sealing itself upon removal of the syringe). Ten mls. ofanhydrous distilled N-methylpyrrolidone (NMP) and 15 mls. of anydrousdistilled tetramethylurea (TMU) were carefully added with the aid ofsyringes. The resulting mixture was stirred and warmed to 40° C. untilall solids had dissolved. The solution was then cooled in a bath of iceand salt to a temperature of -5° C. A small amount of lithium chlorideprecipitation was observed. Recrystallized p,p'-biphenylene dicarbonylchloride (0.4689 gram; 0.001679 mole) was quickly added by means of afunnel to the stirred 2,2'-dibromobenzidine solution. An additional fivemls. of TMU were added through the funnel to the reaction mixture. Thetemperature of the reaction mixture did not rise above a temperature of7° C. After stirring for 60 minutes, the reaction mixture began tothicken and streaming birefringence (but not stir opalescence) wasobserved.

The ice bath was removed from the reaction vessel and the temperaturewas observed to rise to 20° C. in 30 minutes at which point the reactionsolution became milky in appearance. The reaction vessel was placed inan oil bath (40° C.) and the reaction mixture was warmed for 30 minutes.The reaction mixture became clear. The temperature of the reactionmixture rose during the warming to a maximum temperature of 55° C. atwhich temperature the reaction mixture was stirred for one hour. Thereaction product, a 3% wt./vol. polymer solution (three grams of polymerper 100 mls. of reaction solvent) was cooled to 40° C. and poured into200 mls. of ice-water in a blender. The resulting fibrous solid wasfiltered and wahsed (in the blender) twice each with water, acetone andether. The product was dried in a vacuum over at 15 mm. pressure and 90°C. for 18 hours. The product, obtained in 95.4% yield, was a whitefibrous polymeric material having the following recurring structuralunits: ##STR40##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 1 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide was 3.54 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet/visible absorption spectrum for the polymer ofExample 1 (in 5% wt./vol. lithium chloride/dimethylacetamide showed aλ_(max) of 320(ε=75,000).

Elemental analysis for C₂₆ H₁₆ Br₂ N₂ O₂ provided the following:

    ______________________________________                                        % C        % H    % Br     % N   % O                                          ______________________________________                                        Calculated:                                                                           56.97  2.92   29.16  5.11  5.84                                       Found:  56.86  3.25   28.72  5.10  6.07 (by difference)                       ______________________________________                                    

Polymeric films were prepared from the polymeric material of Example 1by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 0.5 to 5% wt./vol., i.e., from 0.5gram to five grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer film was observed to geland a transparent and colorless unoriented film separated from the glassplate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dired in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 1.93.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in air at 220° C.) to about 50% elongation, to effect filmorientation. The resulting films were optically transparent.Birefringence, measured with the aid of a quartz wedge, was 0.293.

EXAMPLE 2

This example illustrates the preparation of poly(2,2'-dinitro-4,4'-biphenylene)-o,o'-dinitro-p,p'-biphenylenedicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.5 grams ofanhydrous lithium chloride and 0.4799 gram (0.001750 mole) ofrecrystallized 2,2'-dinitrobenzidine yellow crystals were added whilemaintaining a positive nitrogen pressure. The reaction vessel was fittedwith a thermometer and a rubber stopple and 30 mls. of anhydrousdistilled N-methylpyrrolidone (NMP) and 20 mls. of anhydrous distilledtetramethylurea (TMU) were carefully added with the aid of syringes. Theresulting mixture was stirred and warmed to 40° C. until all solids haddissolved. The solution was then cooled in a bath of ice and salt to atemerature of -5° C. Recrystallized colorless 2,2'-dinitro-4,4'-biphenyldicarbonyl chloride (0.6460 gram; 0.00175 mole) was quickly added bymeans of a funnel to the stirred 2,2'-dinitrobenzidine solution. Anadditional three mls. of NMP were added through the funnel to thereaction mixture. The temperature of the reaction mixture did not riseabove a temperature of 0° C. After stirring for 30 minutes, there was nonoticeable change in reaction mixture viscosity.

The ice bath was removed from the reaction vessel and the temperaturewas observed to rise to 20° C. in 30 minutes at which point the reactionsolution was heated in stages up to 90° C. over a period of 2.5 hours.

The reaction product, a 3% wt./vol. polymer solution (three grams ofpolymer per 100 mls. of reaction solvent) was cooled to 40° C. andpoured into 200 mls. of ice-water in a blender. The resulting gelatinoussolid was filtered and washed (in the blender) twice each with water,acetone and ether. The product was dried in a vacuum oven at 15 mm.pressure and 90° C. for 18 hours. The polymeric product, obtained in 88%yield, was a dark-yellow powder having the following recurringstructural units: ##STR41##

The inherent viscosity of a polymer solution (0.5 grams of the polymerof Example 2 per 100 mls. of a solution of five grams lithium chlorideper 100 mls. of dimethylacetamide) was 1.40 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet/visible absorption spectrum for the polymer ofExample 2 (in 5% wt./vol. lithium chloride/dimethylacetamide) showed aλ_(max) of 307 nm (ε=38,400) and an absorption peak at 365 nm (ε=3,000).

Elemental analysis for C₂₆ H₁₄ N₆ O₁₀ provided the following:

    ______________________________________                                        % C           % H    % N      % O                                             ______________________________________                                        Calculated:                                                                           54.74     2.47   14.73  28.06                                         Found   54.24     2.60   13.91  29.25 (by difference)                         ______________________________________                                    

Thermogravimetric analysis showed that onset of degradation of thepolymer of Example 2 occurred at 360° C. in nitrogen and at 300° C. inair. Differential scanning calorimetry and thermal mechanical analysisof film samples showed a reproducible transition at about 190° C.

Polymeric films were prepared from the polymeric material of Example 2by casting (onto glass plates) a solution of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer was 5% wt./vol., i.e., five grams polymer per100 mls. of the lithium chloride/dimethylacetamide solution. In eachinstance, the glass plate carrying the puddle-cast polymer solution wasimmersed in water (after most of the solvent had evaporated). Thepolymer film was observed to gel and a transparent, yellow unorientedfilm separated from the glass plate. The resulting film was soaked forseveral hours in water to effect extraction of occluded lithium chlorideand solvent.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in boiling ethylene glycol) to about 60% elongation, toeffect film orientation. The resulting polymeric strips were opticallytransparent. Birefringence, measured with the aid of a quartz wedge, andby index matching, was 0.33. The calculated isotropic refractive indexwas 1.75. Wide-angle X-ray analysis of the birefringent films showedcrystallinity to be less than 10% by weight.

EXAMPLE 3

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-o,o'-dibromo-p,p'-biphenylenedicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 2.0 grams ofanhydrous lithium chloride and 0.7828 gram (0.002289 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple and 20 mls. of anhydrous distilled N-methylpyrrolidone (NMP) and35 mls. of anhydrous distilled tetramethylurea (TMU) were carefullyadded with the aid of syringes. The resulting mixture was stirred andwarmed to 40° C. until all solids had dissolved. The solution was thencooled in a bath of ice and salt to a temperature of 0° C.Recrystallized 2,2'-dibromo-4,4' -biphenylene dicarbonyl chloride(1.0000 gram; 0.002289 mole) was quickly added by means of a funnel tothe stirred 2,2'-dibromobenzidine solution. An additional five mls. ofTMU, at a temperature of 25° C., were added through the funnel to thereaction mixture. The temperature of the reaction mixture rose to 15° C.and then dropped to 4° C. After stirring for 15 minutes, the reactionmixture began to thicken and streaming birefringence (but not stiropalescence) was observed. Stirring was continued for an additional 30minutes at 7° C. and the ice bath was removed from the reaction vessel.The temperature of the reaction mixture rose to 25° C. (in 90 minutes)and the reaction mixture was then slowly heated to 100° C. over atwo-hour period.

The reaction product, a 4% wt./vol. polymer solution (four grams ofpolymer per 100 mls of reaction solvent) was cooled to 40° C. and pouredinto 200 mls. of ice-water in a blender. The resulting fibrous solid wasfiltered and washed (in the blender) twice each with water, acetone andether. The product was dried in a vacuum over at 15 mm. pressure and 90°C. for 18 hours. The product, obtained in 96.6% yield, was a whitefibrous polymeric material having the following recurring structuralunits: ##STR42##

The inherent viscosity of a polymer solution (0.5 grams of the polymerof Example 3 per 100 mls. of a solution of five grams lithium chlorideper 100 mls. of dimethylacetamide) was 2.04 dl./gram at 30° C. Molecularweight determination based on light scattering, indicated 2.72×10⁵, andby gel permeation chromatography, a molecular weight of 5.66×10⁴.Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet/visible absorption spectrum for the polymer ofExample 3 (in 5% wt./vol. lithium chloride/dimethylacetamide) showed aλ_(max) of 305 nm (ε=31,900) and no absorption above 380 nm.

Elemental analysis for C₂₆ H₁₄ Br₄ N₂ O₂ provided the following:

    ______________________________________                                        % C         % H     % Br    % N  % O                                          ______________________________________                                        Calculated:                                                                           44.23   1.99    45.27 3.99 4.52                                       Found:  44.54   2.19    45.25 3.87 4.15 (by difference)                       ______________________________________                                    

Thermogravimetric analysis showed that onset of degradation of thepolymer of Example 3 occurred at 530° C. in nitrogen. Thermal mechanicalanalysis of film samples showed a reproducible transition at about 120°C.

Polymeric films were prepared from the polymeric material of Example 3by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 0.5 to 5% wt./vol., i.e., from 0.5gram to 5 grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (aftermost of the solvent had evaporated). The polymer film was observed togel and a transparent, colorless unoriented film separated from theglass plate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 1.84.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted forstretching between the jaws of a mechanical unidirectional stretcher.Strips were stretched, in some instances, in air at 220° C. and, inother instances, in boiling ethylene glycol. Elongation ranged from 60%to 65%. Infrared dichroism indicated that the films were less than 65%oriented. The films were optically transparent. Birefringence, measuredwith the aid of a quartz wedge, was 0.390. Wide-angle X-ray analysis ofthe birefringent polymer films showed them to be less than 10% by weightcrystalline.

EXAMPLE 4

This example illustrates the preparation of poly(2,2'-dichloro-5,5'-dimethoxy-biphenylene)-o,o'-dibromo-p,p'-biphenylenedicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.5 grams ofanhydrous lithium chloride and 0.6519 gram (0.002082 mole) of sublimed2,2'-dichloro-5,5'-dimethoxybenzidine were added while maintaining apositive nitrogen pressure. The reaction vessel was fitted with athermometer and a rubber stopple and ten mls. of anhydrous distilledN-methylpyrrolidone (NMP) and ten mls. of anhydrous distilledtetramethylurea (TMU) were carefully added with the aid of syringes. Theresulting mixture was stirred and warmed to 40° C. until all solids haddissolved. The resulting orange solution was then cooled in a bath ofice and salt to a temperature of 0° C. A small amount of lithiumchloride precipitation was observed. Recrystallized2,2'-dibromo-4,4'-biphenyldicarbonyl chloride (0.9095 gram; 0.002082mole) was quickly added by means of a funnel to the stirred2,2'-dichloro-5,5'-dimethoxybenzidine solution. An additional ten mls.of TMU (at a temperature of 25° C.) were added through the funnel to thereaction mixture. The temperature of the reaction mixture did not riseabove a temperature of 0° C. After stirring for 30 minutes, theformation of a gelatinous, light-yellow, transparent mass (whichexhibited streaming birefringence but not stir opalescence) wasobserved. Stirring was continued for an additional ten minutes at 8° C.,the stirring was stopped and the ice bath was removed. The temperatureof the reaction mass was observed to rise to 25° C. in 15 minutes, andthe gel became stiffer in consistency. Heating was immediately commencedand an additional 20 mls. of TMU were added to facilitate dissolution ofthe reaction mass. Within 60 minutes the temperature rose to 90° C. andthe gel melted to provide a homogeneous, viscous solution. Heating at90° C. was continued for two hours while stirring vigorously.

The reaction product, a 2.82% wt./vol. light-yellow polymer solution(2.82 grams of polymer per 100 mls. of reaction solvent) was cooled to40° C. and the resulting gelatinous, transparent mass was added to 200mls. of ice-water in a blender. The resulting rubbery solid was filteredand washed (in the blender) twice each with water, acetone and ether.The product was dried in a vacuum oven at 15 mm. pressure and 90° C. for18 hours. The product, obtained in 99.3% yield, was a very pale-yellowfibrous polymeric material having the following recurring structuralunits: ##STR43## The inherent viscosity of a polymer solution (0.5 gramof the polymer of Example 4 per 100 mls. of a solution of five gramslithium chloride per 100 mls. of dimethylacetamide) was 5.75 dl./gram at30° C.

Molecular structure was confirmed by infrared spectroscopy. Elementalanalysis for C₂₈ H₁₈ Br₂ Cl₂ N₂ O₄ provided the following:

    ______________________________________                                        % C        % H     % Br     % Cl   % N   % O                                  ______________________________________                                        Calculated:                                                                           49.66  2.68    23.60  10.47  4.14  9.45                               Found:  49.05  2.95    23.07  --     4.15  --                                 ______________________________________                                    

Polymeric films were prepared from the polymeric material of Example 4by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegms. lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer was 2% wt./vol., i.e., two grams of polymer per100 mls. of the lithium chloride/dimethylacetamide solution. In eachinstance, the glass plate carrying the puddle-cast polymer solution wasimmersed in water (after minimal evaporation of solvent. The polymerfilm was observed to gel and a transparent, colorless unoriented filmseparated from the glass plate. The resulting film was soaked for twodays in water to effect extraction of occluded lithium chloride andsolvent, soaked in acetone and dried in a vacuum oven at 90° C. and 15mm. pressure. Refractive index, measured by interferometry was 1.87.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in air at 220° C.) to about 50% elongation, to effect filmorientation. The stretched films were optically transparent.Birefringence, measured with the aid of a quartz wedge, was 0.24.

Solutions of the polymer of Example 4, in a concentration of 3 to 5%wt./vol., in lithium chloride-containing solvents (e.g.,dimethylacetamide containing lithium chloride) were found to formcolorless, transparent gels which could be melted and resolidifiedwithout thermal degradation. When the molten solutions were poured intomolds or cast into films, solidification was rapid and the solid piecesor films were readily removable. The resulting rubbery solids exhibitedhigh birefringence upon application of very slight stress. Removal ofthe stress was accompanied by instantaneous disappearance of thebirefringent property.

EXAMPLE 5

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-octafluoro-p,p'- biphenylenedicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.5 grams ofanhydrous lithium chloride and 0.4571 gram (0.001338 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple and ten mls. of anhydrous distilled N-methylpyrrolidone (NMP)and ten mls. of anhydrous distilled tetramethylurea (TMU) were carefullyadded with the aid of syringes. The resulting mixture was stirred andwarmed to 40° C. until all solids had dissolved. The solution was thencooled in a bath of ice and salt to a temperature of 0° C. A smallamount of lithium chloride precipitation was observed. Distilled2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenylene dicarbonyl chloride(0.5660 gram; 0.001338 mole) was quickly added by means of a funnel tothe stirred, 2,2'-dibromobenzidine solution. An additional ten mls. ofTMU (at a temperature of 25° C.) were added through the funnel to thereaction mixture. The temperature of the reaction mixture did not riseabove a temperature of 2° C. After stirring for 15 minutes, the reactionmixture began to thicken and streaming birefringence (but not stiropalescence) was observed. Stirring was continued for an additional 30minutes at 4° C. and the ice bath was removed. The temperature of thereaction mixture was observed to rise to 25° C. in 40 minutes at whichpoint the reaction solution was slightly viscous and cloudy inappearance. The reaction mixture was warmed gently for 90 minutes withstirring. The temperature of the reaction mixture rose during thewarming to a maximum temperature of 45° C. at which temperature thereaction solution became homogeneous. Stirring was continued for 18hours at 45° C.

The resulting reaction product, a 3% wt./vol. polymer solution (threegrams of polymer per 100 mls. of reaction solvent) was cooled to 40° C.and poured into 200 mls. of ice-water in a blender. The resultingfibrous solid was filtered and washed (in the blender) twice each withwater, acetone and ether. The product was dried in a vacuum oven at 15mm. pressure and 90° C. for 18 hours. The product, obtained in 87.6%yield, was a white fibrous polymeric material having the followingrecurring structural units: ##STR44##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 5 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 1.68 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet/visible absorption spectrum for the polymer ofExample 5 (in 5% wt./vol. lithium chloride/dimethylacetamide) showed aλ_(max) of 340 nm and an absorption peak at 360 nm (ε=306).

Elemental analysis for C₂₆ H₈ Br₂ F₈ N₂ O2 provided the following:

    ______________________________________                                        % C        % H    % Br    % F  % N  % O                                       ______________________________________                                        Calculated:                                                                           45.11  1.17   23.09 21.97                                                                              4.05 4.61                                    Found:  42.89  1.17   21.86 20.81                                                                              3.76 9.51                                                                          (by difference)                         ______________________________________                                    

Thermogravimetric analysis showed that onset of degradation of thepolymer of Example 5 occurred at 325° C. in nitrogen and at 350° C. inair. Differential scanning calorimetry showed a reproducible transitionat about 155° C.

Polymeric films were prepared from the polymeric material of Example 5by casting (onto glass plates) solutions of the polymeric material in a2% wt./vol. solution of lithium chloride and dimethylacetamide (twograms lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 0.5 to 5% wt./vol., i.e., from 0.5gram to five grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer was observed to gel and atransparent and colorless unoriented film separated from the glassplate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry was 1.74.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips wereoriented by stretching (in air at 200° C.) to an elongation in the rangeof 50 to 55%. The polymeric strips were optically transparent.Birefringence, measured with the aid of a quartz wedge, was 0.35. Stripswere also stretched in methanol at 25° C. to an elongation of 55%.Measurement of birefringence for such stretched films showed abirefringence of 0.44.

EXAMPLE 6

This example illustrates the preparation of poly(2,2',3,3',4,4',6,6'-octafluoro-4,4'-biphenylene)carbohydrazide and thepreparation therefrom of birefringent polymeric films.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.15 grams ofanhydrous lithium chloride and 0.0386 gram (0.001205 mole) of distilledhydrazine were added while maintaining a positive nitrogen pressure. Thereaction vessel was fitted with a thermometer and a rubber stopple andseven mls. of anhydrous distilled N-methylpyrrolidone (NMP) and 12 mls.of anhydrous distilled tetramethylurea (TMU) were carefully added withthe aid of syringes. The resulting mixture was stirred until most of thelithium chloride had dissolved. The solution was then cooled in a bathof ice and salt to a temperature of 0° C. A small amount of lithiumchloride precipitation was observed. Distilled2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenylene dicarbonyl chloride(0.5100 gram; 0.001205 mole) was quickly added by means of a funnel tothe stirred hydrazine solution. An additional four mls. of TMU (at atemperature of 25° C.) were added through the funnel to the reactionmixture. The temperature of the reaction mixture did not rise above atemperature of 5° C. The reaction mixture did not thicken and steamingbirefringence was not observed. Lithium carbonate (0.0890 gram; 0.0024mole) was added to the reaction mixture, stirring was continued for 30minutes at 4° C. and the ice bath was removed. As the temperature of thereaction mixture rose to 25° C. during the subsequent 60 minutes, thereaction solution first became cloudy and, then, a white precipitateformed. Over the next 30 minutes, the reaction mixture was warmed to 40°C. at which time the reaction mixture became homogeneous. The reactiontemperature was raised to 70° C. and maintained for one hour. Noincrease in viscosity was apparent.

The reaction product, a 1.99% wt./vol. polymer solution (1.99 grams ofpolymer per 100 mls. of reaction solvent) was cooled to 40° C. andpoured into 200 mls. of ice-water in a blender. The resulting powderysolid was filtered and washed (in the blender) twice each with water,acetone and ether. The product was dried in a vacuum oven at 15 mm.pressure and 90° C. for 18 hours. The polymeric product, obtained in95.4% yield, was a white solid material having the following recurringstructural units: ##STR45##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 6 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 1.16 dl./gram at 30° C. The molecularstructure of the polymer of Example 6 was confirmed by infraredspectroscopy.

Polymeric films were prepared from the polymeric material of Example 6by casting (onto glass plates) solutions of the polymeric material in a2% wt./vol. solution of lithium chloride and dimethylacetamide (twograms lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 0.5 to 5% wt./vol., i.e., from 0.5gram to five grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle cast polymer solution was immersed in water (afterevaporating the solvent for one hour). The polymer film was observed togel, and a physically weak, cloudy and colorless film separated from theglass plate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure. Thefilms were not of sufficient strength to undergo stretching. Refractiveindex, measured by interferometry, was 1.60.

EXAMPLE 7

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-trans-p,p'-stilbene dicarboxamide andthe preparation therefrom of birefringent polymeric films.

A 250-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 4.88 grams ofanhydrous lithium chloride and 2.1441 grams (0.006269 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple and 45 mls. of anhydrous distilled N-methylpyrrolidone (NMP) and45 mls. of anhydrous distilled tetramethylurea (TMU) were carefullyadded with the aid of syringes. The resulting mixture was stirred andwarmed to 40° C. until all solids had dissolved. The solution was thencooled in a bath of ice and salt to a temperature of -5° C. A smallamount of lithium chloride precipitation was observed. Recrystallizedtrans-p,p'-stilbene dicarbonyl chloride (1.9129 grams; 0.006269 mole)was quickly added by means of a funnel to the stirred2,2'-dibromobenzidine solution. An additional 30 mls. of NMP/TMU mixture(1:1 by weight), at a temperature of 25° C., were added through thefunnel to the reaction mixture. The temperature of the reaction mixturedid not rise above a temperature of 5° C. and then dropped rapidly to-3° C. After stirring for 30 minutes, the reaction mixture began tothicken and streaming birefringence (but not stir opalescence) wasobserved. Lithium carbonate (0.926 gram, 0.01254 mole) was added andstirring was continued for an additional 30 minutes at 0° C.

The ice bath was removed from the reaction vessel, and when thetemperature reached 20° C. (in 30 minutes), the reaction solution hadbecome sufficiently viscous as to begin to climb the shaft of themechanical stirrer. A maximum reaction temperature of 55° C. wasreached. Stirring was stopped and the mixture was heated overnight at atemperature of 55° C. The reaction product, a viscous polymer solutionof 3% wt./vol. concentration (three grams of polymer per 100 mls. ofreaction solvent) was diluted with 130 mls. of 2% wt./vol. lithiumchloride in dimethylacetamide. The resulting polymer solution was pouredinto 200 mls. of ice and water in a blender. The resulting fibrous solidwas filtered and washed (in the blender) twice each with water, acetoneand ether. The product was dried in a vacuum oven at 15 mm. pressure and90° C. for 18 hours. The polymeric product, obtained in 100% yield, wasa very light-yellow fibrous solid having the following recurringstructural units: ##STR46##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 7 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 9.04 dl./gram at 30° C. The molecularweight of the polymer, as determined by light scatterings, was 1.95×10⁶,and be gel permeation chromatography, 8.71×10⁵.

The molecular structure of the polymer was confirmed by infraredspectroscopy. Inspection of the ultraviolet/visible spectrum of thepolymer (in 5% wt./vol. lithium chloride/dimethylacetamide) showed aλ_(max) of 352 nm (ε=66,000); an absorption peak at 368 nm (ε=52,800)and an extremely weak tail at 400 nm.

Elemental analysis for C₂₈ H₁₈ Br₂ N₂ O₂ provided the following:

    ______________________________________                                        % C        % H    % Br     % N   % O                                          ______________________________________                                        Calculated:                                                                           58.56  3.16   27.83  4.88  5.57                                       Found:  58.50  3.22   27.94  4.87  5.47 (by difference)                       ______________________________________                                    

Thermogravimetric analysis showed that the onset of degradation of thepolymer of Example 7 occurred at 470° C. in nitrogen and at 515° C. inair. Differential scanning calorimetry and thermal mechanical analysisof film samples detected a reproducible transition at about 225° C.

Polymeric films were prepared from the polymeric material of Example 7by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 1 to 5% wt./vol., i.e., from onegram to five grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer was observed to gel and atransparent and colorless unoriented film separated from the soakedglass plate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 2.03.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in air at 220° C.) to about 55 to 55% elongation, to effectfilm orientation. The stretched films were optically transparent.Infrared dichroism indicated that the stretched films were less than 65%by weight oriented; the modulus was 3.9×10⁶ p.s.i. Wide-angle X-rayanalysis of the films showed crystallinity to be less than 10% byweight. Birefringence, measured with the aid of a quartz wedge, was0.589.

Solutions of the polymer of Example 7 in lithiumchloride/dimethylacetamide, as aforedescribed, were formed into extrudedfilms by the "wet-jet" method whereby the solution of polymer isextruded into an aqueous coagulation bath for gelling of the polymermaterial. The resulting transparent, colorless film strips were soakedin water and cut to about 1 to 2 inches (25.4 to 50.8 mm.) for testing.The partially oriented strips of film produced by the extrusion werefurther oriented by stretching in the manner described in the Exampleshereof. Stretching was effected in air at a temperature of 180° C.Elongation was to the break point, in the range of about 40% to 50%. Thestretched strips were optically transparent. Measurement ofbirefringence utilizing a quartz wedge provided a birefringence value of0.977. Measurement by resort to interferometry provided a value of0.865.

EXAMPLE 8

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-trans-α-bromo-biphenylene dicarboxamideand the preparation therefrom of birefringnet polymeric films.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, a pressure-equalizing dropping funnel, a nitrogeninlet tube and calcium chloride drying tube) was heated whilesimultaneously flushing the vessel with nitrogen. After the reactionvessel had cooled to room temperature, 1.5 grams of anhydrous lithiumchloride and 0.4779 gram (0.001397 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple and 15 mls. of anhydrous distilled N-methylpyrrolidinone (NMP)and five mls. of anhydrous distilled tetramethylurea (TMU) werecarefully added with the aid of syringes. The resulting mixture wasstirred and warmed to 40° C. until all solids had dissolved. Thesolution was then cooled in a bath of ice and salt to a temperature of0° C. A small amount of lithium chloride precipitation was observed.Recrystallized α-bromo-p,p'-stilbene dicarbonyl chloride (0.5366 gram;0.001397 mole) was quickly added by means of a funnel to the stirred2,2'-dibromobenzidine solution. An additional ten mls. of TMU (at atemperature of 25° C.) were added through the funnel to the reactionmixture. The temperature of the reaction mixture did not rise above atemperature of 4° C. After stirring for 15 minutes, the reaction mixturebegan to thicken and streaming birefringence (but not stir opalescence)was observed. Stirring was continued for an additional 30 minutes at 4°C.

The ice bath was removed from the reaction vessel and the temperaturewas observed to rise to 25° C. in 90 minutes at which point the reactionmixture had become sufficiently viscous as to climb the shaft of themechanical stirrer. Over the next 90 minutes, the very pale-yellowreaction mass was gently warmed with intermittant stirring; the maximumtemperature reached was approximately 70° C.

The reaction product, a 3% wt./vol. polymer solution (three grams ofpolymer per 100 mls. of reaction solvent) was cooled to 40° C. andpoured into 200 mls. of ice-water in a blender. The resulting fibroussolid was filtered and washed (in the blender) twice each with water,acetone and ether. The product was dried in a vacuum oven at 15 mm.pressure and 90° C. for 18 hours. The product, obtained in 95.4% yield,was a light-yellow fibrous polymeric material having the followingrecurring structural units: ##STR47##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 8 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 7.81 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Elementalanalysis for C₂₈ H₁₇ N₂ Br₃ O₂ provided the following:

    ______________________________________                                        % C         % H    % Br    % N  % O                                           ______________________________________                                        Calculated:                                                                           51.478  2.604  36.724                                                                              4.289                                                                              4.90                                        Found:  51.17   2.80   34.82 4.15 7.06 (by difference)                        ______________________________________                                    

Polymeric films were prepared from the polymeric material of Example 8by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 0.5 to 5% wt./vol., i.e., from 0.5gram to 5 grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer was observed to gel and atransparent and colorless unoriented film separated from the soakedglass plate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 2.07.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in air at 220° C.) to about 60% to 65% elongation, to effectfilm orientation. The stretched strips were optically transparent.Birefringence, measured with the aid of a quartz wedge, was 0.680.

Solutions of the polymer of Example 8 in lithiumchloride/dimethylacetamide, as aforedescribed, were formed into extrudedfilms by the "wet-jet" method whereby the solution of polymer isextruded into an aqueous coagulation bath for gelling of the polymermaterial. The resulting transparent, colorless film strips were soakedin water and cut to about 1 to 2 inches (25.4 to 50.8 mm.) for testing.The partially oriented strips of film produced by the extrusion werefurther oriented by stretching in the manner described in the Exampleshereof. Stretching was effected in air (at a temperature of 180° C.) tothe break point, in the range of about 40% to 50% elongation. Thestretched film strips were optically transparent. Measurement ofbirefringence utilizing a quartz wedge provided a birefringence value of0.955. Measurement by resort to interferometry provided a value of0.849.

EXAMPLE 9

This example illustrates the preparation of poly(2,2'-dibromo-4,4'-biphenylene)-α,α'-dimethylmuconamide and thepreparation therefrom of birefringent polymeric films.

A 50-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, a pressure-equalizing dropping funnel, a nitrogeninlet tube and calcium chloride drying tube) was heated whilesimultaneously flushing the vessel with nitrogen. After the reactionvessel had cooled to room temperature, 0.4 gram of anhydrous lithiumchloride and 0.8519 gram (0.00249 mole) of sublimed2,2'-dibromobenzidine were added while maintaining a positive nitrogenpressure. The reaction vessel was fitted with a thermometer and a rubberstopple and ten mls. of anhydrous distilled N-methylpyrrolidone (NMP)were carefully added with the aid of a syringe. The resulting mixturewas stirred and warmed to 40° C. until all solids had dissolved. Thesolution was then cooled in a bath of ice and salt to a temperature of0° C. with formation of some lithium chloride precipitate. A solution ofrecrystallized α,α'-dimethyl muconyl chloride (0.5157 gram; 0.002491mole) in six mls. of anhydrous, distilled tetrahydrofuran(THF) was addedto the dropping funnel through a rubber stopper with a syringe. Theα,α'-dimethyl muconyl chloride/THF solution, the temperature of whichwas 25° C., was added dropwise over five minutes to the cold2,2'-dibromobenzidine solution while stirring moderately. The additionfunnel was rinsed with six mls. of NMP which was also added dropwise tothe reaction mixture in order to prevent the temperature of the reactionmixture from rising above 1° C. After stirring for one hour, duringwhich time the solution turned lemon-yellow (but did not thicken), 0.354gram of solid lithium carbonate was added all at once to the reactionmixture. Within ten minutes noticeable thickening was observed, andafter an additional 20 minutes, at 20° C., the viscosity increasedfurther. The ice bath was removed from the reaction vessel and thetemperature of the reaction mixture was allowed to rise to 25° C. over aone-hour period during which time a thick paste had formed. Thetemperature of the reaction mixture was increased to 65° C. over thenext 20 minutes producing a mixture which could no longer be stirred.Additional heating for 18 hours at 55° C. without stirring produced atransparent, light-yellow viscous polymer solution. The reactionproduct, a 5.36% wt./vol. polymer solution (5.36 grams of polymer per100 mls. of reaction solvent) was observed to exhibit considerablestreaming birefringence upon application of low mechanical stress; stiropalescence was not, however, observed.

The polymer solution was poured into a blender containing 200 ml. ofice-water and the resulting fibrous solid was filtered and washed (inthe blender) twice each with water, acetone and ether. The product wasdried in a vacuum oven at 15 mm. pressure and 90° C. for 18 hours. Theproduct, obtained in 94.7% yield, was a white fibrous polymeric materialhaving the following recurring structural units: ##STR48##

The inherent viscosity of a polymer solution (0.5 grams of the polymerof Example 9 per 100 mls. of a solution of five grams lithium chlorideper 100 mls. of dimethylacetamide) was 4.69 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet/visible absorption spectrum for the polymer ofExample 9 (in 3% wt./vol. lithium chloride/dimethylacetamide showed aλ_(max) of 333 nm(ε=33,600) and an extremely weak tail at 400 nm.

Elemental analysis for C₂₀ H₁₆ Br₂ N₂ O₂ provided the following:

    ______________________________________                                        % C         % H    % Br    % N  % O                                           ______________________________________                                        Calculated:                                                                           50.448  3.387  33.562                                                                              5.883                                                                              6.72                                        Found:  50.09   3.45   34.17 5.72 6.57 (by difference)                        ______________________________________                                    

Thermogravimetric analysis showed that the onset of degradation occurredat 360° C. in nitrogen and at 310° C. in air. Differential scanningcalorimetry and thermal mechanical analysis of film samples showed areproducible transition at about 185° C.

Polymeric films were prepared from the polymeric material of Example 9by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 2 to 4% wt./vol., i.e., from twograms to four grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer film was observed to geland a transparent and colorless unoriented film separated from the glassplate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 1.91.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical stretcher and were unidirectionally stretched,successively, in steam, acetone and boiling ethylene glycol (all ofwhich function as plasticizers). The strips were stretched to anelongation of from 35% to 45%. The film strips were further elongated(up to 60%) by stretching in air at 200° C. The stretched strips wereoptically transparent. Optical retardation was measured with acalibrated quartz wedge; film thickness was measured with a micrometer.Birefringence, measured by means of a quartz wedge, was 0.40.

EXAMPLE 10

This example illustrates the preparation ofpoly-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]-trans-p,p'-stilbenedicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 100 ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, nitrogen inlet tube and calcium chloride dryingtube) was heated while simultaneously flushing the vessel with nitrogen.After the reaction vessel had cooled to room temperature, 1.5 grams ofanhydrous lithium chloride and 0.5171 gram (0.001615 mole) ofrecrystallized 2,2'-bis(trifluoromethyl)-benzidine were added whilemaintaining a positive nitrogen pressure. The reaction vessel was fittedwith a thermometer and a rubber stopple and ten mls. of anhydrousdistilled N-methylpyrrolidone (NMP) and ten mls. of anhydrous distilledtetramethylurea (TMU) were carefully added with the aid of syringes. Theresulting mixture was stirred and warmed to 40° C. until all solids haddissolved. PG,64 The solution was then cooled to a bath of ice and saltto a temperature of -5° C. A small amount of lithium chlorideprecipitation was observed. Recrystallized trans-p,p'-stilbenedicarbonyl chloride (0.4923 gram; 0.001615 mole) was carefully added bymeans of a funnel to the stirred 2,2'-bis(trifluoromethyl)-benzidinesolution. An additional 10 mls. of TMU, at a temperature of 0° C., wereadded through the funnel to the reaction mixture. The temperature of thereaction mixture did not rise above a temperature of 5° C. and thendropped rapidly to -3° C. After stirring for 30 minutes, the reactionmixture began to thicken and streaming birefringence (but not stiropalescence) was observed. Stirring was continued for an additional 30minutes at 0° C.

The ice bath was removed from the reaction vessel, and when thetemperature reached 20° C. (in 30 minutes), the reaction solution hadbecome very viscous. Over the next 75 minutes, the completely colorless,transparent solution was warmed to 72° C. After stirring at thistemperature for the next 18 hours, the mixture was cooled to 40° C. Theresulting polymer solution was poured into 200 mls. of ice and water ina blender. The resulting fibrous solid was filtered and washed (in theblender) twice each with water, acetone and ether. The product was driedin a vacuum oven at 15 mm. pressure and 90° C. for 18 hours. Thepolymeric product, obtained in 99.5% yield, was a very light-yellowfibrous solid having the following recurring structural units: ##STR49##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 11 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 4.735 dl./gram at 30° C. Themolecular structure of the polymer was confirmed by infraredspectroscopy.

Elemental analysis for C₃₀ H₁₈ F₆ N₂ O₂ provided the following:

    ______________________________________                                        % C        % H     % F     % N   % O                                          ______________________________________                                        Calculated:                                                                           65.22  3.28    20.64 5.07  5.79                                       Found:  64.54  3.76    19.04 4.85  7.81 (by difference)                       ______________________________________                                    

Thermogravimetric analysis showed that the onset of degradation of thepolymer of Example 11 occurred at 500° C. in nitrogen and at 410° C. inair. Differential scanning calorimetry and thermal mechanical analysisof film samples detected a reproducible transition at about 185° C.

Polymeric films were prepared from the polymeric material of Example 10by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 1.0 to 5% wt./vol., i.e., from 1.0gram to five gramps polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer film was observed to geland a transparent and colorless unoriented film separated from the glassplate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 1.997.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical unidirectional stretcher. The strips werestretched (in air at 220° C.) to about 60 to 65% elongation, to effectfilm orientation. The stretched films were optically transparent.Birefringence, measured with the aid of a quartz wedge, was 0.537.

Solutions of the polymer of Example 10 in lithiumchloride/dimethylacetamide, as aforedescribed, were formed into extrudedfilms by the "wet-jet" method whereby the solution of polymer isextruded into an aqueous coagulation bath for gelling of the polymermaterial. The resulting transparent, colorless film strips were soakedin water and cut to about 1 to 2 inches (25.4 to 50.8 mm.) for testing.The partially oriented strips of film produced by the extrusion werefurther oriented by stretching in the manner described in the Exampleshereof. Stretching was effected to an elongation of less than 20%. Thestretched strips were optically transparent. Infrared dichroismindicated that the films were 92% oriented. Measurement of birefringenceutilizing a quartz wedge provided a birefringence value of 0.879.

EXAMPLE 11

This example illustrates the preparation ofpoly-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]-2,2'-dimethoxy-4,4'-biphenyldicarboxamide and the preparation therefrom of birefringent polymericfilms.

A 100-ml. reaction vessel (a resin-making kettle equipped with amechanical stirrer, a pressure-equalizing dropping funnel, a nitrogeninlet tube and calcium chloride drying tube) was heated whilesimultaneously flushing the vessel with nitrogen. After the reactionvessel had cooled to room temperature, 3.0 grams of anhydrous lithiumchloride and 0.4328 gram (0.001352 mole) of recrystallized2,2'-bis(trifluoromethyl)benzidine were added while maintaining apositive nitrogen pressure. The reaction vessel was fitted with athermometer and a rubber stopple and 20 mls. of anhydrous distilledN-methylpyrrolidinone (NMP) and 20 mls. of anhydrous distilledtetramethylurea (TMU) were carefully added with the aid of syringes. Theresulting mixture was stirred and warmed to 40° C. until all solids haddissolved. The solution was then cooled in a bath of ice and salt to atemperature of -5° C. A small amount of lithium chloride precipitationwas observed. Recrystallized 2,2'-dimethoxy-4,4'-biphenyldicarbonylchloride (0.4586 gram; 0.001352 mole) was quickly added by means of afunnel to the stirred 2,2'-bis(trifluoromethyl)benzidine solution. Anadditional 20 mls. of TMU (at a temperature of 0° C.) were added throughthe funnel to the reaction mixture. The temperature of the reactionmixture did not rise above a temperature of 5° C. After stirring for 30minutes, the reaction mixture began to thicken and turned milk-like inappearance. Stirring was continued for an additional 30 minutes at 0° C.

The ice bath was removed from the reaction vessel and the temperaturewas observed to rise to 20° C. in 30 minutes at which point the reactionmixture was viscous and opaque. Over the next 75 minutes, the opaquereaction mass was gently warmed to 40° C. at which point it becametransparent. After stirring at this temperature for the next 18 hours,the reaction mixture was cooled to 30° C. and poured into 400 mls. ofice-water in a blender. The resulting fibrous solid was filtered andwashed (in the blender) twice each with water and ether. The product wasdried in a vacuum oven at 15 mm. pressure and 90° C. for 18 hours. Theproduct, obtained in 99.3% yield, was an off-white fibrous polymericmaterial exhibiting solubility in acetone or tetrahydrofuran and havingthe following recurring structural units: ##STR50##

The inherent viscosity of a polymer solution (0.5 gram of the polymer ofExample 11 per 100 mls. of a solution of five grams lithium chloride per100 mls. of dimethylacetamide) was 1.69 dl./gram at 30° C.

Molecular structure was confirmed by infrared spectroscopy. Inspectionof the ultraviolet visible spectrum of the polymer (in 5% wt./vol.lithium chloride/dimethylformamide) showed a λ_(max) of 316 nm(ε=2.59×10³).

Elemental analysis for C₃₀ H₂₀ F₆ N₂ O₄ provided the following:

    ______________________________________                                        % C        % H     % F     % N   % O                                          ______________________________________                                        Calculated:                                                                           61.34  3.43    19.41 4.77  10.89                                      Found:  59.82  3.51    18.70 4.62  13.35 (by difference)                      ______________________________________                                    

Thermogravinetic analysis showed that the onset of degradation of thepolymer of Example 11 occurred at 470° C. in nitrogen and at 440° C. inair. Differential scanning colorimetry detected a reproducibletransition at about 180° C.

Polymeric films were prepared from the polymeric material of Example 11by casting (onto glass plates) solutions of the polymeric material in a5% wt./vol. solution of lithium chloride and dimethylacetamide (fivegrams lithium chloride per 100 mls. of dimethylacetamide). Theconcentration of polymer ranged from 1% to 5% wt./vol., i.e., from 1.0gram to 5 grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. In each instance, the glass platecarrying the puddle-cast polymer solution was immersed in water (afterminimal evaporation of solvent). The polymer was observed to gel and atransparent and colorless unoriented film separated from the soakedglass plate. The resulting film was soaked for several hours in water toeffect extraction of occluded lithium chloride and solvent, soaked inacetone and dried in a vacuum oven at 90° C. and 15 mm. pressure.Refractive index, measured by interferometry, was 1.73.

Solutions of the polymer of Example 11 in lithiumchloride/dimethylacetamide, as aforedescribed, were formed into extrudedfilms by the "wet-jet" method whereby the solution of polymer isextruded into an aqueous coagulation bath for gelling of the polymermaterial. The resulting transparent, colorless film strips were soakedin water and cut to about 1 to 2 inches (25.4 to 50.8 mm.) for testing.The partially oriented strips of film produced by the extrusion werefurther oriented by stretching in the manner described in the Exampleshereof. Stretching was effected in air (at a temperature of 180° C.) toan elongation of less than 20%. The stretched film strips were opticallytransparent. Infrared dichroism indicated that the films were 92%oriented. Measurement of birefringence utilizing a quartz wedge provideda birefringence value of 0.586.

EXAMPLE 12

This example illustrates the preparation ofpoly-2,2'(bis-trifluoromethyl)-4,4'-biphenylene carboxamide, i.e., apolymer having the following recurring structural units: ##STR51## Thepolymer was prepared by polymerization (as described hereinafter) of themonomer 2,2'-bis(trifluoromethyl)-4-amino-4-biphenylcarboxylic acidhaving the structure ##STR52## This monomer was prepared from2,2'-bis(trifluoromethyl)-4,4'-dinitro-biphenyl by partial reductionusing sodium hydrogen sulfide to provide2,2'-bis(trifluoromethyl)-4-nitro-4'-amino-biphenyl; diazotization ofthe resulting compound followed by reaction with sodium triiodide toprovide 2,2'-bis(trisfluoromethyl)-4-nitro-4'-iodo-biphenyl; aRosenmund-von Braun reaction using cuprous cyanide inN-methyl-2-pyrrolidone to provide2,2'-bis(trifluoromethyl)-4-nitro-4'-cyano-biphenyl; hydrolysis using63% sulfuric acid to provide2,2'-bis(trifluoromethyl)-4-nitro-4'-biphenyl carboxylic acid; andcatalytic reduction using palladium on carbon to provide the aforesaidmonomer 2,2'-bis(trifluoromethyl)-4-amino-4'-biphenyl carboxylic acid.

Into a dry 250-ml. reaction vessel (a Schlenk tube equipped with amagnetic stirring bar and a condenser topped with a calcium chloridedrying tube) was placed 2.0 gram (0.0057 mole) of2,2'-bis(trifluoromethyl)-4-amino-4'-biphenyl carboxylic acid, preparedin the manner aforedescribed. Thionyl chloride (10 mls.) was added andthe reaction mixture was refluxed for two hours. After cooling to roomtemperature, excess thionyl chloride was removed by aspirator vacuum.The vacuum was released under an argon atmosphere and dry ether (150mls.) was added. Gaseous hydrochloric acid (dried through a calciumchloride drying tube) was bubbled through the stirred contents of thereaction vessel which was cooled in an ice bath. When the resultingeither solution had become saturated, the solid reaction product wasallowed to settle under argon. Reaction solvent was removed by suctionfiltration through a fritted filter tube and the solid reaction productwas washed three times with ether. The product was dried under highvacuum and the filter tube and magnetic stirring bar were removed. Thereaction vessel was fitted with a mechanical stirrer and was cooled in abath of dry ice and acetone. Tetramethylurea (TMU, 20 mls.) was added tothe gently stirred solid which froze and caused cessation of stirring.An ice bath was substituted for the dry ice/acetone bath and stirringwas again commenced. During the next hour, TMU (40 mls.) was added. Thereaction mixture was allowed to warm to room temperature and was stirredovernight. The resulting colorless viscous solution was heated to 50° C.for two hours and, then, at 80° C. for five hours. The resulting hotsolution was poured into water in a blender and the polymer precipitatewas collected by vacuum filtration. The product was then dissolved intetrahydrofuran and stirred overnight. The resulting solution was workedup in two batches, in each instance by pouring the solution into water(700 mls.) in a blender and collecting the polymeric product by vacuumfiltration. The polymer was washed with water and was dried under highvacuum to yield a combined amount of polymer of 1.76 grams (93% yield).The inherent viscosity of the polymer in 5% wt./vol. lithiumchloride/dimethyl acetamide at 30° C. was 5.0 dl./gram.Thermogravimetric analysis showed the onset of degradation in nitrogenat 450° C. and in air at 440° C. Molecular structure was confirmed byinfrared spectroscopy. Refractive index of a film prepared from thepolymer was 1.6367, measured by Brewster angle. A stretched film of thepolymer showed a birefringence of 0.24 measured by using a quartz wedge.

EXAMPLE 13

This example illustrates the preparation ofpoly-3-methoxy-4,4'-stilbenylene carboxamide, i.e., a polymer havingrecurring units of the following structure: ##STR53##

The polymer of this example was prepared by the polymerization (asdescribed hereinafter) of the monomer4-[2-(4-aminophenyl)ethenyl]-3-methoxybenzoic acid having the structure##STR54## This monomer was prepared from 4-carbomethoxy-2-methoxybenzyltriphenylphosphinium bromide by: A Wittig reaction of the4-carbomethoxy-2-methoxybenzyl triphenylphosphinium bromide withp-nitro-benzaldehyde to providemethyl-3-methoxy-4-[2-(4-nitrophenyl)ethenyl]benzoate; basic hydrolysisusing potassium hydroxide to provide the corresponding acid,3-methoxy-4-[2-(4-nitrophenyl)ethenyl]benzoic acid; and a basicreduction using ferrous sulfate heptahydrate and ammonium hydroxide toprovide the corresponding aforedescribed amino compound,4-[2-(4-aminophenyl)ethenyl]-3-methoxybenzoic acid.

Into a dry 100-ml. reaction vessel (a Schlenk tube fitted with amagnetic stirrer bar, a condenser topped with a calcium chloride dryingtube and a nitrogen inlet) was placed, under nitrogen, 0.248 gram of4-[2-(4-aminophenyl) ethenyl]-3-methoxybenzoic acid (prepared asaforedescribed.) Thionyl chloride (four mls.) was added and theresulting solution was brought to reflux at which time the solutionbecame homogeneous. After one hohur, the solution was concentrated toone third of its volume. Dry benzene was added under nitrogen and thesolution was again concentrated, nearly to dryness. Dry benzene (50mls.) was then added and the cooled solution was saturated with gaseoushydrochloric acid. After stirring for two hours at room temperature, theprecipitate was allowed to settle. The benzene was filtered off using afritted filter tube under nitrogen and the solid product was washedthree times with benzene and was dried under vacuum. The magneticstirrer was replaced with a mechanical stirrer and the reaction vesselwas cooled in dry ice/acetone bath. TMU (4 mls.) was added and theproduct immediately solidified. The dry ice/acetone bath was replaced byan ice bath and stirring was commenced to provide a homogeneousorange-colored solution. Additional TMU (two mls.) was added and after30 minutes the solution was thick and cloudy. The solution remainedcloudy after introduction of an additional quantity (eight mls.) of TMU.The ice bath was removed and additional TMU was added to bring finalvolume to 20 milliliters. The resulting solution was stirred at roomtemperature for six hours and then at 60° C. overnight.Dimethylacetamide was added to aid in transfer of the solution into ablender containing water. The polymer which precipitated was collectedon a glass filter and was washed three times with water and once withacetone. The polymer showed solubility in hot sulfuric acid.

EXAMPLE 14

This example illustrates the preparation of 1:3poly(3'-methoxy-4,4'-stilbenylenecarboxamido-co-2,2'-bis-trifluoromethyl-4,4'-biphenylene carboxamide),i.e., a polymer containing the following repeating units: ##STR55##

Into a dry 100-ml. reaction vessel (a Schlenk tube fitted with amagnetic stirring bar and a condenser with a calcium chloride dryingtube attached to an argon inlet) were added 0.318 gram (0.00091 mole) of4-amino-2,2'-bistrifluoromethyl-4'-carboxybiphenyl and 0.081 gram(0.00030 mole) of 4-[2-(4-aminophenyl)ethenyl]-3-methoxybenzoic acid.Thionyl chloride (five mls.) was added and the resulting solution wasrefluxed for one hour. After cooling to room temperature, the thionylchloride was removed under reduced pressure. Dry benzene (20 mls.) anddry ether (7 mls.) were added and the solution was cooled in an icebath. Dry hydrochloric acid gas was bubbled through the solution for 45minutes. Ether (15 mls.) was added and the resulting precipitate wasallowed to settle. The solvent was removed by suction filtration througha fritted filter tube and the resulting solid product was washed sixtimes with ether. The precipitate was dried under high vacuum and thefilter tube and magnetic stirrer were removed. The reaction vessel wasfitted with a mechanical stirrer. After cooling the flask in a dryice/acetone bath, TMU (four mls.) with 4% lithium chloride was added andthe product immediately froze. An ice bath was then substituted for thedry ice/acetone bath, and as the solution warmed, stirring commenced.Additional TMU (six mls.) was added and the solution was carried at 0°C. for one hour. The solution became very thick and dark in color. Themixture was allowed to warm to room temperature and was stirred untilthickening and gelation caused stirring to cease. N-methylpyrolidinone(NMP, eight mls.) and TMU (six mls.) were added to the resulting gel andstirring was restarted. The reaction mixture was heated in an oil bathat 60° C. for four hours. After cooling to room temperature, thesolution was poured into water stirring in a blender. A polymericprecipitate was collected by vacuum filtration and was washed twice withwater and once with ether. The product was vacuum dried in an oven toyield 0.380 gram (99%) of a yellow fibrous solid. The inherent viscosityof the polymer (dissolved in 6% wt./vol. lithiumchloride/dimethylacetamide at 30° C.) was 4.737 dl./gram.

EXAMPLE 15

This example illustrates the preparation of 1:9poly(3-methoxy-4,4'-stilbenylenecarboxamide-co-2,2'-bis-trifluoromethyl-4,4'-biphenylene carboxamide),i.e., a copolymer having the following recurring units: ##STR56##

Into a 100-ml. Schlenk reaction vessel (fitted with a magnetic stirringbar and condenser having a calcium chloride tube attached to an argoninlet on top) were added 0.60 gram (0.00172 mole) of4-amino-2,2'-bistrifluoromethyl-4'-carboxybiphenyl and 0.050 gram(0.00186 mole) of 4-[2-(4-aminophenyl)ethenyl]-3-methoxybenzoic acid.Thionyl chloride (six mls.) was added to the reaction solution and thesolution was refluxed for two hours. After cooling to room temperature,the thionyl chloride was removed under reduced pressure. Dry benzene(tem mls.) and dry ether (ten mls.) were added through a cannular andthe resulting solution was cooled in an ice bath. Hydrochloric gas(dried through a calcium chloride tube) was bubbled through the solutionfor one hour. After the polymeric precipitate had settled, reactionsolvent was removed by suction filtration through a filtering tube andthe solid product was washed three times with ether. The precipitate wasdried under high vacuum and the filter stick and magnetic stirrer wereremoved. The reaction vessel was fitted with a mechanical stirrer. Aftercooling the flask in a dry ice/acetone bath, TMU (four mls.) with 4%lithium chloride was added and the product immediately froze. An icebath was then substituted for the dry ice/acetone bath, and as thesolution warmed, stirring started. Addditional TMU (eight mls.) wasadded and the solution was stirred at 0° for one hour. After 30 minutes,additional TMU (three mls.) was added. Undissolved material was brokenup with the stirring bar and additional TMU was added for a total volumeof 30 milliliters. The solution was stirred at room temperature for twohours and at 70° C. overnight. The cooled solution was poured into waterstirring in a blender. The resulting precipitate was collected by vacuumfiltration washed twice with water and once with ether. The product wasvacuum dried to yield 0.496 gram (78%) of a pale yellow fibrous solid.The inherent viscosity of the polymer dissolved in 5% wt./vol. lithiumchloride/dimethylacetamide at 30° C. was 4.94 dl./gram.Thermogravimetric analysis showed that the onset of degradation occurredin nitrogen at 440° C. Molecular structure was confirmed by infraredspectroscopy. The refractive index of a film of the resulting copolymer,measured by Brewster angle, was 1.7015. Birefringence of a stretchedfilm, measured by means of a quartz wedge, was 0.23.

EXAMPLE 16

For purposes of comparison with the substituted polyamides of thepresent invention, an unsubstituted polyamide was prepared and evaluatedin the following manner.

A solution polymerization reaction for the production ofpoly(p-benzamide) was conducted in accordance with the followingreaction scheme: ##STR57##

A 50-ml. reaction vessel (a resin-making kettle equipped with mechanicalstirrer, nitrogen inlet tube and calcium chloride drying tube) washeated while simultaneously flushing the vessel with nitrogen. After thereaction vessel had cooled to room temperature, 40 mls, of anhydrousdistilled tetramethyl urea (TMU), 8.04 grams (0.04 mole) ofvacuum-distilled p-thionylaminobenzoyl chloride and 0.52 gram (0.012mole) of lithium chloride were added while maintaining a positivenitrogen pressure. The resulting reaction mixture was stirred for tenminutes at room temperature and 1.68 grams (0.04 mole) of lithiumhydroxide monohydrate were added while vigorously stirring. The reactionmixture was then stirred for one hour at room temperature. After aperiod of seven additional minutes, the reaction mixture became cloudyand was observed to thicken. The polymeric reaction product, after 20minutes, thickened sufficiently to adhere the shaft of the mechanicalstirrer. After one-half hour, the reaction mixture, which could not bestirred, was heated. An additional quantity (14 mls.) of TMU was addedat which point the reaction mixture still could not be stirred. Thereaction mixture was then heated to 130° C. without stirring. After twohours of heating at 130° C., pliability of polymeric reaction massincreased and the product appeared to have partially dissolved. Thereaction product was stored in the reaction vessel overnight and waswashed with water, filtered and washed with acetone then ether. Theproduct, poly(p-benzamide) was dried in a vacuum oven at 80° C. for twohours.

The inherent viscosity of a polymer solution of poly(p-benzamide) insulfuric acid was 1.60 dl./gram at 30° C.

Polymeric films of poly(p-benzamide) were prepared by casting a solutionof the polymeric material in a 5% wt./vol. solution of lithium chlorideand dimethylacetamide (five grams lithium chloride per 100 mls. ofdimethylacetamide). The concentration of polymer was 5% wt./vol., i.e.,five grams polymer per 100 mls. of the lithiumchloride/dimethylacetamide solution. The cast polymer film was dried ina vacuum oven at 90° C. (30 in. Hg) overnight. The polymer film was anopaque, white flexible film. Additional films were formed bypuddle-casting the solution as aforedescribed onto glass plates. In eachinstance, the glass plate carrying the puddle-cast polymer solution wasimmersed in water (after most of the solvent had evaporated). Thepolymer film which separated from the glass plate was a tough,transparent, flexible film. The resulting film was soaked for severalhours in water to effect extraction of occluded lithium chloride andsolvent.

Stretched polymeric films were prepared in the following manner.Water-swollen films (obtained by soaking the polymer films for severalhours for removal of occluded lithium chloride and solvent asaforedescribed) were cut into strips. The strips were mounted betweenthe jaws of a mechanical stretcher and were unidirectionally stretched,successively, in steam and in air (at 200° C.). The strips werestretched to an elongation of approximately 10%. The resulting stretchedfilms were clouded in appearance. Optical retardation was measured witha calibrated quartz wedge; film thickness was measured with amicrometer. Birefringence, measured by means of a quartz wedge, was0.23.

EXAMPLE 17

Geometric indices were determined for the repeating units of polymericmaterials having the following structure ##STR58## wherein each X ishydrogen or a substituent as set forth in the following TABLE I. In thecase of each recurring unit, the eccentricity factor (1+e_(L))/(1+e_(T))was calculated and is reported in TABLE I. Bond and group polarizabilitytensors were utilized to calculate a polarizability matrix for eachrepeat unit, the diagonalized form of the matrix providing the X, Y andZ contributions to the unit polarizability ellipsoid. Axialpolarizabilities, i.e., X, Y and Z, were utilized to calculatelongitudinal and transverse eccentricities of each repeat unit, thus,reflecting its symmetry.

Eccentricity values were calculated utilizing the following procedure. Apolarizability and a corresponding orthogonal coordinate system isassigned to each segment of the polymer repeat unit. Literature valuesfor group polarizabilities are utilized from the literature, or wherenot available, are constructed from bond polarizabilities. AvailableDenbigh values were utilized herein for all calculations. Bondpolarizabilities are utilized to connect segments where necessary. Todetermime the overall polarizability of the repeat unit, the coordinatesystem of the segment at one end of the repeat unit is made coincidentwith that of the adjacent segment by means of the appropriaterotation(s). This procedure is repeated on each successive segment untilthe last segment is reached. Mathematically, this means that the matrixof one segment must be pre- and post-multiplied by a transformationmatrix:

    α.sub.1 '=Υα.sub.1 Υ.sup.-1

where α₁ is the polarizability of segment 1; Υ is the transformationmatrix; Υ⁻¹ is the inverse of Υ; and α₁ ' is the polarizability ofsegment 1 in the coordinate system of segment 2. The value of α₁ ' isthen added to α₂ and the transformation repeated. The repeat unitpolarizability matrix is diagonalized, thus, providing a repeat unitpolarizability ellipsoid with three semi-axes, i.e., α_(xx), α_(yy), andα_(zz), where α_(xx) is the major polarizability and is coincident withthe polymer backbone.

Literature-reported values of 25° and 31°, respectively, were utilizedin all calculations as representing the dihedral angle between thephenyl and carbonyl moieties and the dihedral angle between the phenyland amino moieties, respectively. Experimentally determined values forthe dihedral angle between each X-substituted phenyl moiety wereutilized in all calculations and are reported in TABLE I. Mean diametervalues, D, and length, L, were obtained from space-filling molecularmodels.

                  TABLE I                                                         ______________________________________                                         (Dihedral Angle)Substituent X                                                            (D)DiameterMean                                                                        (L)Length                                                                              ##STR59##                                                                              G                                      ______________________________________                                        H          4.49     21.35    1.061     0.989                                  (20°)                                                                  F          4.61     21.35    1.206    1.21                                    (60°)                                                                  Cl         4.78     21.35    1.348    1.23                                    (72°)                                                                  Br         4.83     21.35    1.388    1.24                                    (75°)                                                                  I          4.91     21.35    1.428    1.26                                    (85°)                                                                  CF.sub.3   4.90     21.35    1.496    1.33                                    (80°)                                                                  CH.sub.3   4.76     21.35    1.330    1.25                                    (71°)                                                                  ______________________________________                                    

From the data presented in TABLE I will be observed the influence of thenature of the X substituent relative to a hydrogen atom as regards thereported dihedral angle and resulting substantial noncoplanarity betweeninterbonded phenyl rings. Differences in mean diameter and influence ofthe nature of X substituents on mean diameter and eccentricity factor,and correspondingly, geometric index G will also be observed. Thus, itwill be noted that the largest substituents, i.e., --CF₃ and --Isubstituents, corresponded with the largest dihedral angles betweeninterbonded phenyl groups or the highest non-coplanarity and,accordingly, recurring units having such substituents show highgeometric index values.

For purposes of comparison, geometric index G was calculated for therepeat unit of poly(p-phenylene)terephthalamide having the followingstructure and the results thereof are reported in TABLE II. Dihedralangle values of 25° and 31° were utilized for purposes of calculation asin the case of the repeat units of EXAMPLE 17. ##STR60##

                  TABLE II                                                        ______________________________________                                        (D)DiameterMean                                                                         (L)Length                                                                                            G                                            ______________________________________                                        4.43     12.45         0.978    0.621                                         ______________________________________                                    

As can be observed from inspection of the data reported in TABLES I andII, the geometric indices for the repeat units of the materials setforth in TABLE I are considerably higher than the geometric indexcalculated for poly(p-phenylene)terephthalamide of TABLE II.

EXAMPLE 18

Geometric indices for the recurring units of polyamides having thefollowing structure were calculated. Each X substituent was as indicatedin TABLE III. Dihedral angles from the literature were utilized in suchcalculations. Calculated geometric indices were compared with values oftheoretical maximum birefringence for the polymeric materials, reportedin TABLE III. Theoretical maximum birefringence values (Δn_(max)) wereobtained by plotting the orientation function, calculated from infrareddichroism, against experimental birefringence and extrapolating to 100%orientation. The results are set forth in TABLE III. ##STR61##

                  TABLE III                                                       ______________________________________                                        Substituent X                                                                 (Dihedral Angle)  G      Δn.sub.max                                     ______________________________________                                        --Br              1.20   1.20                                                 (75°)                                                                  --CF.sub.3        1.17   0.98                                                 (80°)                                                                  ______________________________________                                    

From the data presented in TABLE III, it will be seen that high valuesof geometric index G corresponded with high values of Δn_(max). Forpurposes of comparison, the theoretical maximum birefringence value(Δn_(max)) for the recurring unit of poly(p-phenylene)terephthalamide(having a G value of 0.621 as shown in TABLE II) was also determined.The resulting Δn_(max) value of 0.83 forpoly(p-phenylene)terephthalamide was higher than would be predicted fromthe geometric index value, G, of 0.621. This is believed to be theresult of the highly crystalline nature of thepoly(p-phenylene)terephthalamide material, whereas the geometric index Greflects the inherent anisotropy of an isolated chain independent ofsuch macroscopic properties as morphology, density, color or the like.

The enhanced optical anisotropy exhibited by the preferredsubstituted-aromatic polyamide materials utilized in the optical deviceshereof is believed to be the result of the rigid, rod-like uniaxialmolecular structure of such materials and the amorphous/crystallineratio thereof. This ratio typically ranges from about 10:1 to about20:1. In the case of highly unidirectionally oriented phenyl-typepolyamides this ratio generally will be in the range of about 0.3:1. Thepresence of crystallites is generally detrimental in polymeric materialsadapted to utilization in optical devices owing to light scattering anddiminished transparency. The non-coplanarity between substitutedbiphenyl rings, resulting from sterically bulky groups on the orthopositions of interbonded phenyl rings, raises the amorphous/crystallineratio to a range of from about 10:1 to about 20:1. This permits thefabrication of highly oriented films and fibers exhibiting hightransparency in addition to high birefringence. The ring-substitutedbiphenyl polyamides additionally exhibit enhanced solubility and can befabricated into colorless films or fibers where desired.

EXAMPLE 19

A light-polarizing device utilizing a highly birefringent polyamidematerial was constructed in the following manner.

A sheet of birefringent material was prepared from the polyamide ofExample 10, i.e.,poly[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]-trans-p,p'-stilbenedicarboxamide. The sheet was prepared by the "wet-jet" extrusion methoddescribed in Example 10. The resulting extruded polymer, in the form ofa partially oriented transparent colorless film, was soaked in water andcut into strips. The strips were then further oriented by stretching inair in the manner also described in Example 10. A strip of thebirefringent polymer (having perpendicular and parallel indices ofrefraction, respectively, of approximately 1.72 and 2.34 and anapproximate thickness of 25 microns) was embossed by contacting onesurface of the strip with a brass prismatic plate heated to atemperature of 180° C. and pressing the heated plate onto the surface ofthe film so as to provide a pristmatic layer of birefringent materialgenerally shown in FIG. 6 as layer 42.

Onto a sheet of transparent isotropic glass material of approximatelyone-mm. thickness was poured a layer of polychlorinated biphenyl, anisotropic material having an index of refraction of 1.654, available asAroclor 1260 from Monsanto Company, St. Louis, Mo. The prismatic layerof birefringent material, prepared as aforesaid, was placed onto thelayer of Aroclor. The prismatic layer was covered with a second layer ofAroclor so as to embed the prismatic layer in Aroclor material. A secondsheet of glass was placed onto the Aroclor so as to sandwich thebirefrigent and Aroclor materials between the two pieces of glass. Theresulting polarizer device was tested for its light polarizingproperties by placing the test device and a second polarizer into thepath of a light beam and by observing the attenuation of light resultingfrom rotation of the respective polarizers.

What is claimed is:
 1. A film- or fiber-forming polymer comprisingrecurring units of the formula ##STR62## wherein R¹ is hydrogen, alkyl,aryl, alkaryl or aralkyl and A is a divalent radical selected from thegroup consisting of:(1) a radical ##STR63## where each U is asubstituent other than hydrogen, each W is hydrogen or a substituentother than hydrogen, and each p is an integer from 1 to 3, said U andW_(p) substitution being sufficient to provide the aromatic nuclei ofsaid radical with a non-coplanar molecular configuration with respect toeach other; and (2) a radical ##STR64## where each of Y and Z ishydrogen or a substituent other than hydrogen and each t is an integerfrom 1 to 4, with the proviso that when each said Z is hydrogen, atleast one said Y substituent is a substituent other than hydrogenpositioned on the corresponding nucleus ortho with respect to the##STR65## moiety of said radical, said Z and Y_(t) substitution beingsufficient to provide the aromatic nuclei of said radical with anon-coplanar molecular configuration with respect to each other.
 2. Thefilm- or fiber-forming polymer of claim 1 wherein said divalent radicalA is said radical having the formula ##STR66## wherein each U is asubstituent other than hydrogen, each W is hydrogen or a substituentother than hydrogen and each p is an integer from 1 to 3, said U andW_(p) substitution being sufficient to provide the aromatic nuclei ofsaid radical with a non-coplanar molecular configuration with respect toeach other.
 3. The film- or fiber-forming polymer of claim 2 wherein R¹is hydrogen.
 4. The film- or fiber-forming polymer of claim 2 whereinsaid divalent radical is a radical having the formula ##STR67## whereineach U is a substituent other than hydrogen.
 5. The film- orfiber-forming polymer of claim 4 wherein each U substituent is selectedfrom the group consisting of halogen, nitro, alkoxy andsubstituted-alkyl.
 6. The film- or fiber-forming polymer of claim 5wherein each U substituent is bromo.
 7. The film- or fiber-formingpolymer of claim 5 wherein each U substituent is nitro.
 8. The film- orfiber-forming polymer of claim 5 wherein each U substituent istrifluoromethyl.
 9. The film- or fiber-forming polymer of claim 8wherein R¹ is hydrogen.
 10. The film- or fiber-forming polymer of claim1 wherein said divalent radical A is a radical having the formula##STR68## where each of Y and Z is hydrogen or a substituent other thanhydrogen and each t is an integer from 1 to 4, with the proviso thatwhen each said Z is hydrogen, at least one said Y substituent is asubstituent other than hydrogen positioned on the corresponding nucleusortho with respect to the ##STR69## moiety of said radical, said Z andY_(t) substitution being sufficient to provide the aromatic nuclei ofsaid radical with a non-coplanar molecular configuration with respect toeach other.
 11. The film- or fiber-forming polymer of claim 10 whereinR¹ is hydrogen.
 12. The film- or fiber-forming polymer of claim 10wherein each said Z is hydrogen, each said t is the integer one and eachcorresponding Y substituent is a substituent other than hydrogenpositioned on the ##STR70## moiety of the radical.
 13. The film- orfiber-forming polymer of claim 12 wherein each said Y substituent isselected from the group consisting of halogen, nitro and alkoxy.
 14. Thefilm- or fiber-forming polymer of claim 10 wherein each Y is hydrogen,each t is the integer four, one said Z is hydrogen, and the remainingsaid Z substituent is halogen.
 15. The film- or fiber-forming polymer ofclaim 14 wherein said halogen is bromo.
 16. A molecularly orientedbirefringent polymer in the form of a film or fiber comprising recurringunits of the formula ##STR71## wherein R¹ is hydrogen, alkyl, aryl,alkaryl or aralkyl and A is a divalent radical selected from the groupconsisting of:(1) a radical ##STR72## where each U is a substituentother than hydrogen, each W is hydrogen or a substituent other thanhydrogen and each p is an integer from 1 to 3, said U and W_(p)substitution being sufficient to provide the aromatic nuclei of saidradical with a non-coplanar molecular configuration with respect to eachother; and (2) a radical ##STR73## where each of Y and Z is hydrogen ora substituent other than hydrogen and each t is an integer from 1 to 4,with the proviso that when each said Z is hydrogen, at least one said Ysubstituent is a substituent other than hydrogen positioned on thecorresponding nucleus ortho with respect to the ##STR74## moiety of saidradical, said Z and Y_(t) substitution being sufficient to provide thearomatic nuclei of said radical with a non-coplanar molecularconfiguration with respect to each other.
 17. The polymeric film orfiber of claim 16 wherein said divalent radical A is said radical havingthe formula ##STR75## wherein each U is a substituent other thanhydrogen, each W is hydrogen or a substituent other than hydrogen andeach p is an integer from 1 to 3, said U and W_(p) substitution beingsufficient to provide the aromatic nuclei of said radical with anon-coplanar molecular configuration with respect to each other.
 18. Thepolymeric film or fiber of claim 17 wherein R¹ is hydrogen.
 19. Thepolymeric film or fiber of claim 17 wherein said divalent radical is aradical having the formula ##STR76## wherein each U is a substituentother than hydrogen.
 20. The polymeric film or fiber of claim 19 whereineach U substituent is selected from the group consisting of halogen,nitro, alkoxy and substituted-alkyl.
 21. The polymeric film or fiber ofclaim 20 wherein each U substituent is bromo.
 22. The polymeric film orfiber of claim 20 wherein each U substituent is nitro.
 23. The polymericfilm or fiber of claim 20 wherein each U substituent is trifluoromethyl.24. The polymeric film or fiber of claim 23 wherein R¹ is hydrogen. 25.The polymeric film or fiber of claim 16 wherein said divalent radical Ais a radical having the formula ##STR77## where each of Y and Z ishydrogen or a substituent other than hydrogen and each t is an integerfrom 1 to 4, with the proviso that when each said Z is hydrogen, atleast one said Y substituent is a substituent other than hydrogenpositioned on the corresponding nucleus ortho with respect to the##STR78## moiety of said radical, said Z and Y_(t) substitution beingsufficient to provide the aromatic nuclei of said radical with anon-coplanar molecular configuration with respect to each other.
 26. Thepolymeric film or fiber of claim 25 wherein R¹ is hydrogen.
 27. Thepolymeric film or fiber of claim 25 wherein each said Z is hydrogen,each said t is the integer one and each corresponding Y substituent is asubstituent other than hydrogen positioned on the ##STR79## moiety ofthe radical.
 28. The polymeric film or fiber of claim 27 wherein eachsaid Y substituent is selected from the group consisting of halogen,nitro and alkoxy.
 29. The polymeric film or fiber of claim 25 whereineach Y is hydrogen, each t is the integer four, one said Z is hydrogen,and the remaining said Z substituent is halogen.
 30. The polymeric filmor fiber of claim 29 wherein said halogen is bromo.